Center Specific Reports July 2003

July 2003 Center-Specific Reports
July 2003 CSR Fast Facts Timeline	National Reports Programs Report OPO Report

This file is an archive report from July 2003.

This page details the conventions used by the SRTR for analyses included in the Transplant Center-Specific Reports.

Table of Contents

Introduction

Center Summary

Table 1. Waitlist Activity

On Waitlist at Start
Additions
Removals
On Waitlist at End of Period
Additional Observations and Caveats

Table 2. Characteristics of Waitlist Patients

Race
Ethnicity
Age
Gender
Blood Type
Previous Transplants
Peak Panel Reactive Antibody (Kidney, Pancreas, and Kidney/Pancreas Programs Only)
Primary Diagnosis Group (Not Shown for Pancreas and Kidney/Pancreas Programs)
Years Since Diabetes Onset (Pancreas Programs Only)
Recipient Medical Urgency Status at Waitlist (Liver and Heart Programs Only)

Table 3. Transplant and Mortality Rates among Waitlist Patients

Count on Waitlist at Start
Person Years
Transplant Rate (per year on waitlist)
Expected Transplant Rate
P-value
Ratio of Observed to Expected Events
95% Confidence Interval
Comparison of Rates
Number of deaths
Death Rate (per year on waitlist)
Expected Death Rate

Table 4. Waitlist Activity and Patient Vital Status at 6, 12, and 18 Months Since Waitlisting

Table 5. Percent Transplanted (Excludes Living Donor Recipients) for Waitlist Patients at This Center

Table 6. Time to Transplant for Waitlist Candidates

Table 7. Transplant Recipient Characteristics

Patient Count
Race
Ethnicity
Age
Gender
Blood Type
Previous Transplants
Peak Panel Reactive Antibody (Kidney, Pancreas and Kidney/Pancreas Programs Only)
Body Mass Index
Primary Diagnosis Group (Not Shown for Pancreas and Kidney/Pancreas Programs)
Recipient Medical Urgency Status at Waitlist (Liver and Heart Programs for Patients with Deceased Donors Only)
Recipient Medical Urgency Status at Transplant (Liver and Heart Programs for Patients with Deceased Donors Only)
Recipient Medical Condition at Transplant
Recipient Life Support Status at Transplant

Table 8. Summary for Characteristics of Transplant Donors

Patient Count
Cause of Death
Age
Race
Ethnicity
Gender
Blood Type
Expanded Criteria Donors

Table 9. Summary for Characteristics of Transplant Operations

Patient Count
Cold Ischemic Time (Deceased Donor Transplants Only)
Relation With Donor (Living Donor Transplants Only)
Level of Mismatch
Procedure Type
Dialysis in First Week After Transplant
Sharing (Deceased Donor Transplants Only)
Median Length of Stay

Table 10. Graft Survival Rates

Number of Transplants
Graft Survival
Expected Graft Survival
Ratio of Observed to Expected Graft Failures
95% Confidence Interval
P-value
Comparison of Rates
Follow-Up Days Reported
Maximum Days of Follow-Up

Table 11. Patient Survival Rates

Number of Patients
Patient Survival
Expected Patient Survival
Ratio of Observed to Expected Deaths
95% Confidence Interval
P-Value
Comparison of Rates
Follow-Up Days Reported
Maximum Days of Follow-Up

Technical Notes on Computing Expected Patient or Graft Survival

Model Fitting Methods
Missing Data
Notes on Diagnosis, Ischemia Time, and Other Continuous Variables
Calculation of Individual Expected Survival

References

Introduction

There are 11 tables and a summary table that report statistics for individual transplant center programs. When the description below refers to the statistics for a "center", it actually indicates the statistics for a particular transplant program (specific organ) at that center. The statistics in these tables are based on data available from the Organ Procurement and Transplant Network (OPTN) as of April 30, 2003. These tables report organ procurement and transplantation activities. Generally, the same conventions that have been used previously by the OPTN to tabulate donors, organs, transplants, and transplant operations were used here. These tables are described individually below. A table is suppressed if there are no patients for that specific table for your center.

Center Summary

The center summary table presents selected statistics for your center that can be found in greater detail in Tables 1-11. These statistics provide summary data as a reference for frequently asked questions.

Table 1. Waitlist Activity

Table 1 presents the movement of candidates on and off the waitlist between January 1, 2001 and December 31, 2002. Candidates are placed according to the center at which they were waitlisted. This information is given for the center and, for purposes of comparison, for the U.S. as a whole. The data are presented as counts of candidates for a given center (the leftmost pair of columns for the two time periods reported) and as percentages of the candidates on the waitlist at the start of the period (the last three columns give statistics for the center, the OPTN Region, and the U.S.). The three columns on the right of the table report values as percentages to allow comparison of patient counts at the center, OPTN region, and national levels of aggregation.

The data exclude candidates who received a living-donor transplant without ever having been waitlisted and candidates waitlisted for pancreatic islets.

On Waitlist at Start
The number of patients at the center at the start of a period is defined as the number of patients who were placed on the waitlist before midnight, of the previous day and who had not been removed as of that time.

Additions
The number of additions to the waitlist for transplantation at the center for a given period is the number of candidates whose listing date was during that period.

Removals
The removals of candidates from the waitlist are reported according to the reason for removal (e.g. "Deteriorated", meaning the condition of the patient had deteriorated to the point that they had been removed from the waitlist). The available removal codes are: transferred to another center, received living transplant, received cadaveric transplant, died, medically unsuitable, deteriorated, recovered, and other reasons. The removals are counted only if they occur during the period.

Percentages are relative to the waitlist at the start of the period, dividing the number of candidates added/removed/still on the waitlist during the period specified by the number of candidates on the waitlist at the beginning of the period. The result is multiplied by 100 to produce the percentage.

On Waitlist at End of Period
The number of candidates on the waitlist at the end of a period is the number of patients on the waitlist at the end of the prior period, plus the additions during the period, minus the removals during the period. The number of candidates in a program at the end of the first period is the same as the number of candidates at the beginning of the second period.

The percentage of additions and removals are added to and subtracted from, respectively, the 100% on the waitlist at the start of the period to yield the percentage on the waitlist at the end of the period. Note that if more candidates join the waitlist than are removed during a period, the "percentage" of patients on the waitlist at the end of the period will be greater than 100%. For example, if the U.S. percentage for kidney candidates on the waitlist at the end of the period were 108.8%. The additional 8.8% would represent the growth of the kidney waitlist during the period. Note that it is possible for the number of additions and removals during a period to exceed the number on the waitlist at the start of the period, so that the percent of additions and removals can be greater than 100%.

Additional Observations and Caveats
The number of candidates removed from the waitlist for various reasons at a given program is dependent upon data submitted to the OPTN and provided to the SRTR. For example, it is possible that a candidate is reported as removed from the pancreas waitlist for a living donor transplant, even though no such transplants were performed at that center, according to information contained in the OPTN database. We have observed only a small number of such data anomalies, which are likely due to discrepancies in the data reported by programs on different data collection forms. Data used for transplant tables later in the report are derived from different elements in the database and, therefore, counts of waitlist removals for transplant and counts of reported transplants may not always correspond.

Table 2. Characteristics of Waitlist Patients

Table 2 shows the distribution of various characteristics among waitlisted candidates for each organ in a particular center, in each OPTN region, and nationwide. Candidates are placed according to the center at which they were waitlisted. These data are presented both for new candidates whose listing date was between January 1, 2002 and December 31, 2002 inclusive and for all candidates who were on the waitlist on December 31, 2002. All data are obtained from files of current waitlistings or previous waitlist removals.

At the top of each column, the "(N = )" shows the number of candidates whose data were used to calculate the percentages in that column. The percentages are reported for each of the characteristics described below. The percentages within each characteristic add to 100%, except for rounding anomalies. Candidates with missing information are in the "Unknown" or "Other" categories.

Race
The percentage of recipients in each of five race categories: Asian/Pacific Islander, Black, White, a combined group for other race, and unknown is shown.

Ethnicity
The percentage of Hispanic and non-Hispanic recipients is reported.\

Age
Age was determined as of the date of waitlist for each patient. The percentage of patients in each of several age ranges is reported.

Gender
The percentage of male and female recipients is reported.

Blood Type
The percentage of recipients by ABO type (O, A, B, AB) is reported. Recipients with ABO type A, A1, or A2 were classified as A. Recipients with ABO type AB, A1B, or A2B were classified as AB.

Previous Transplants
The percentage of candidates whose waitlist forms indicated that they had received any previous transplant is reported.

Peak Panel Reactive Antibody (Kidney, Pancreas, and Kidney/Pancreas Programs Only)
The recipients' highest panel reactive antibody (PRA) while on the waitlist is shown for candidates for kidney, pancreas, or kidney/pancreas transplant. The percentage of candidates in each of several PRA ranges (0-9, 10-79, 80+) is reported.

Primary Diagnosis Group (Not Shown for Pancreas and Kidney/Pancreas Programs)
The percentage of patients in each of the major categories of primary cause of organ failure is reported. The major categories for each organ are shown below. Primary diagnosis group is not shown for pancreas and kidney/pancreas programs because virtually all such patients receive a transplant for diabetes mellitus.

Kidney

Glomerular diseases
Tubular and interstitial disease
Polycystic kidney disease
Congenital, familial, and metabolic kidney diseases
Diabetes mellitus
Renovascular & vascular diseases
Neoplasms
Hypertensive nephrosclerosis
Retransplant/graft failure
Other kidney diseases
Missing

Liver

Acute hepatic necrosis
Non-cholestatic cirrhosis
Cholestatic liver disease/cirrhosis
Biliary atresia
Metabolic diseases
Malignant neoplasms
Other
Missing

Intestine

Short gut syndrome
Functional bowel problem
Retransplant/graft failure
Other
Missing

Heart

Cardiomyopathy
Coronary artery disease
Retransplant/graft failure
Valvular heart disease
Congenital heart disease
Other
Missing

Lung

Congenital disease
Retransplant/graft failure
Primary pulmonary hypertension
Cystic fibrosis
Idiopathic pulmonary fibrosis
Alpha-1-antitrypsin deficiency
Emphysema/Chronic obstructive pulmonary disease (COPD)
Other
Missing

Heart-Lung

Congenital disease
Retransplant/graft failure
Primary pulmonary hypertension
Cystic fibrosis
Idiopathic pulmonary fibrosis
Alpha-1-antitrypsin deficiency
Emphysema/Chronic obstructive pulmonary disease (COPD)
Other
Missing

Years Since Diabetes Onset (Pancreas Programs Only)
The number of years since the onset of diabetes is reported.

Recipient Medical Urgency Status at Waitlist (Liver and Heart Programs Only)
The recipients' medical urgency status when registered on the waitlist is shown for liver and heart programs. The percentage of recipients in each of status type (Livers: Status 1, 2A, 2B, 3, Temporarily Inactive; Hearts: Status 1, 1A, 1B, 2, Temporarily Inactive) is reported.

Beginning on February 27, 2002 candidates for liver transplants were classified by MELD or PELD score rather than medical urgency status. However, Status 1 and "temporarily inactive" candidates were still grouped by their respective statuses. MELD and PELD scores were computed based on the candidates’ laboratory measures at the time of the wait listing. If not all of the necessary laboratory values were measured, the candidate was assigned a MELD or PELD of 6, depending on the candidate’s age. The following groups appear for liver candidates after February 27, 2002: Status 1, MELD 6-10, MELD 11-20, MELD 21-30, MELD 31-40, PELD 10 or less, PELD 11-20, PELD 21-30, PELD greater than 30, and Temporarily Inactive.

Table 3. Transplant and Mortality Rates among Waitlist Patients

Table 3 reports transplant and mortality rates for patients on the waiting list between January 1, 2001 and December 31, 2002, along with the expected rates and corresponding p-values. For liver and kidney programs, there are two sets of transplant statistics: one for all transplant and another for transplants from deceased donors. Only transplants from deceased donors are included for other programs. The information in this table is for all patients on the waitlist at this center at any time during the reported interval. For the purpose of comparison, corresponding rates for the second interval in this center's OPTN region and the United States as a whole are also reported.

Count on Waitlist at Start
The total number of patients on the waitlist at 12:00 am the morning of the beginning of the period is reported.

Person Years
Since candidates may be waitlisted for all or only part of a full year, person years of the patients on the waitlist for the whole period is reported. Person years are calculated as days and converted to fractional years for each patient. The number of days is calculated from the latter of the start date of the period and the date of first wait listing, until the earlier of the date of removal from the waitlist and the end of the period. The person years for each candidate in the program are summed to yield the total person years.

Transplant Rate (per year on waitlist)
The rate shown is calculated by dividing the number of waitlist patients removed from the waitlist whose reason for waitlist removal was listed as receipt of a transplant by the total number of person years.

Expected Transplant Rate
The expected transplant rate is calculated as the number of waitlist patients expected to have been removed for receipt of a transplant divided by the number of person years. The expected number was calculated using a Cox proportional hazards model. Data for all organs were adjusted by age, blood type, days on the waiting list prior to the start date, and previous transplantation. Data for heart and liver are also adjusted by medical urgency status. Kidney data were also adjusted by peak PRA and the interaction between previous transplantation and peak PRA.

Beginning on February 27, 2002 candidates for liver transplants were classified by MELD or PELD score rather than medical urgency status. However, Status 1 and "temporarily inactive" candidates were still grouped by their respective statuses. In the transplant rate models, the match MELD/PELD score was used. This means that exceptions, such as those for Hepatocellular Carcinoma (HCC), were taken into account when granted. Some candidates that were Status 2A on 2/27/02 were left in that status for up to thirty more days, so they were grouped as Status 2A for the transplant rate model.

Ratio of Observed to Expected Events
For statistical comparisons, it is appropriate to compare the number of deaths or transplants observed during follow-up period to the number of deaths or transplants that would be expected during follow-up period. A ratio greater than 1.00 indicates that there were more deaths or transplants at the center than would have been expected based on the national experience, while a ratio less than 1.00 indicates that there were fewer deaths or transplants at the center than would have been expected based on the national experience. For example, a ratio of 1.20 indicates that the death or transplant rate at the center was, on average, 20% higher than the national rate. A ratio equal to 1.00 indicates that the death or transplant rates at the center are the same as the national death or transplant rates.

Random variation
The ratio reported is an estimate of the true ratio of death or transplant rates at the center relative to the national transplant rates. A ratio different from 1.00 indicates that the true death or transplant rates at the center differ from the national death or transplant rates. However, the value of the ratio varies from year to year above and below the true ratio due to random variation. Thus, the ratio could differ from 1.00 due to random variation, rather than due to a true difference between the death rates or transplant rates at the center and in the nation. Both the p-value and the confidence interval, discussed below, are designed to help in the interpretation of the ratio in the face of such random fluctuations.

95% Confidence Interval
The 95% confidence interval for the ratio of observed to expected transplants gives a range of plausible values for the true ratio of center to national death or transplant rates, in light of the observed ratio. The true ratio lies within this range 95% of the time. The confidence interval is a measure of how precisely we are able to estimate the ratio. If the 95% confidence interval includes 1.00, then the ratio is not significantly different than 1.00, which means that the death or transplant rates at the center are not significantly different than the national rates (p<0.05).

P-value
The p-value measures the statistical significance (or evidence) for testing the (two-sided) hypothesis that the difference between the actual and expected death rate or transplant rate is 0. A p-value less than or equal to 0.05 indicates that the difference between the actual and expected death rate or transplant rate is probably real and is not due to random chance, while a p-value greater than 0.05 indicates that the difference could plausibly be due to random chance. The p-value was calculated by testing whether the observed number of deaths or transplants was greater or less than the expected number of deaths or transplants at a center, based on the Poisson distribution for the observed number of failures. These values are not shown if there is no expected death rate or transplant rate calculated.

How do rates at this center compare to those in the nation?
This line indicates whether the actual transplant rate or death rate is statistically different than the expected transplant rate or death rate based on the p-value on the previous line. If the p-value is less than or equal 0.05 then this line reads "Statistically Higher" or "Statistically Lower" depending on whether the actual transplant rate or death rate is higher or lower than the expected transplant rate or death rate. If the p-value is greater than 0.05 then this line reads "Not Significantly Different". These values are not shown if there is no expected transplant rate or death rate calculated.

Number of deaths
The number of deaths that occurred among patients on the waitlist during the period is reported. Only deaths reported on the waitlist removals data forms are included in this calculation. This data source is not designed to provide complete ascertainment of mortality and represents only the mortality reported prior to removal from the waitlist for other reasons.

Death Rate (per year on waitlist)
The rate shown is calculated by dividing the number of waitlist patients removed from the waitlist whose reason for waitlist removal was death by the number of person years.

Expected Death Rate
The expected death rate is calculated as the number of deaths expected to have occurred divided by the number of person years. The expected number was calculated using a Cox proportional hazards model. The expected death rates for all organs are adjusted by age, race, ethnicity, gender, blood type, primary disease, days on the waiting list prior to the start date, and diagnosis code (except for pancreas and kidney/pancreas). The rates for heart and liver are also adjusted by medical urgency status.

Beginning on February 27, 2002 candidates for liver transplants were classified by MELD or PELD score rather than medical urgency status. However, Status 1 and "temporarily inactive" candidates were still grouped by their respective statuses. In the models for waitlist mortality, the MELD and PELD scores were computed based on the candidates’ laboratory measures for each point in time. If not all of the necessary laboratory values were measured, the candidate was assigned a MELD or PELD of 6, depending on the candidate’s age. Additionally, whether or not the MELD/PELD score was missing was adjusted for in the model.

Table 4. Waitlist Activity and Patient Vital Status at 6, 12, and 18 Months Since Waitlisting

Table 4 shows the status of waitlisted patients at three time points after waitlisting: 6, 12, and 18 months. Patients included are those who were put on the waitlist at this center between July 1, 2000 and June 30, 2001. For purposes of comparison, corresponding data for the U.S. are also reported at the same time points.

Patient waitlist status was determined by using waitlist removal codes. If a patient had not been removed from the waitlist at each time point they were considered to be alive on the waitlist. For patients whose removal codes corresponded to receiving a transplant, status was determined from follow-up records collected after the transplant. If a patient had a removal code for transplantation, but did not have any transplant or follow-up records associated with that candidacy, they were placed under their appropriate transplant heading, subheading "status unknown."

Percentages indicated on the lines of the table above "TOTAL" (patients on the waitlist who are alive, have died, have been removed without transplant, have received living and cadaveric transplants, and are lost or transferred) add to 100% and reflect data from all patients waitlisted in during the period. It is important to note that these percentages reflect the full range of possible outcomes since placement on the waitlist. For example, if 3.5% died following cadaveric transplant at 18 months after waitlisting indicates that this percentage of all waitlisted candidates had received a cadaveric transplant and subsequently died by 18 months after waitlisting. A patient who falls into this category may have fallen into the category of living with a cadaveric transplant at an earlier time period.

The last four lines of the table contain summary death and transplant percentages. The total percent dead includes all patients reported to have died by that follow-up point, including those who die both before or after a transplant. The following line adds to this total those who were removed from the waitlist due to deteriorating medical condition, but were not reported as having died.

The total removed for transplant shows those patients listed as removed from the waiting list for transplant on or before this time, regardless of current status of the transplant. The last line shows the subset of these with whose transplant is still functioning at the point in time.

The death counts reported here include only those deaths reported as waitlist removals due to death or as deaths on transplant follow-up forms. These data sources are not designed to count all deaths, so the deaths reported here represent an under-ascertainment of mortality. Similarly, the graft failures reported here are based on transplant follow-up forms and do not include failures that occur after patients are reported as lost to follow-up.

For liver programs, additional tables provide the same data stratified by medical urgency status at listing.

Table 5. Percent Transplanted (Excludes Living Donor Recipients) for Waitlist Patients at This Center

Table 5 gives the percentages of patients who received a transplant at the specified times (1 month, 1 year, 2 years, and 3 years after waitlisting) among those who were placed on the waitlist from Jan 1, 1997 - Dec 31, 1999. This information is given for the center and, for purposes of comparison, for the U.S. as a whole. The data exclude patients who were removed from the waitlist with a removal code indicating transplant from a living donor. Patients waitlisted for pancreatic islets are also excluded.

This analysis includes patients whose waitlist status was temporarily inactive and patients who spent periods of time in temporarily inactive status. The statistics are calculated as simple fractions and the analysis does not censor patients if they were removed for reasons other than receiving a transplant. Thus, patients who die before receiving a transplant are counted at all times as not having received a transplant. Each percentage is calculated among all patients and separately for different classifications of: race, ethnicity, age, gender, blood type, previous transplant, primary disease, peak PRA (kidney, pancreas, and kidney/pancreas programs only), years since diabetes onset (pancreas and kidney/pancreas programs only) and medical urgency status (heart and liver programs only).

The percentage shown is calculated as: 100 x (number of patients placed on the waitlist between 1/1/1997 and 12/31/1999 who received a transplant prior to a specified number of months after waitlisting) / (total number of patients placed on the waitlist between 1/1/1997 and 12/31/1999).

The national statistics double count patients with multiple listings in order to be comparable to the center statistic, which counts each waitlist at the center, but only the transplant at this center.

Table 6. Time to Transplant for Waitlist Candidates

Table 6 gives the median (50th percentile) waiting time until transplant (both cadaveric and living related transplants) for patients who were placed on the waitlist between Jan 1, 1997 and June 30, 2002, as well as the 5th, 10th, 25th and 75th percentile waiting times. All percentiles are shown only when applicable. The information in this table is for all patients placed on the waitlist at this center during the applicable time period. For purposes of comparison, corresponding times to transplant at each percentile in this center's OPTN region and the U.S. as a whole are also reported. Patients with multiple waitlistings are counted multiple times in this analysis.

Waiting time until transplant is calculated as the time (in months) after a candidate is placed on the waitlist, by which the corresponding percent of all patients initially waitlisted had been removed from the waitlist for receiving a transplant. A Kaplan-Meier model was used with censoring on a) December 31, 2002 for those registrations still waiting on that date; and b) the date of removal from the waiting list for recovery, or c) the date of removal from the waiting list for a transfer. If a cell is blank then less than that percentage of patients placed had received a transplant by the end of follow-up.

Table 7. Transplant Recipient Characteristics

Table 7 summarizes the characteristics of transplant recipients who received a transplant between January 1, 2002 and December 31, 2002 at this center, with corresponding average values among recipients in this center's OPTN region and the U.S. as a whole. Table 7 is divided into cadaveric and living donor transplants for kidney, liver and lung programs. For all other programs, only data for cadaveric transplants are shown. The percentages are reported for each characteristic. The percentages within each characteristic add to 100% except for rounding anomalies. Candidates with missing information are in the "Unknown" or "Missing" categories.

Patient Count
The total numbers of patients who received transplants during this period at this center, in this center's OPTN region, and in the U.S. as a whole are reported. The summaries of the patient characteristics in Table 7 are based on the patient population counts.

Race
The percentage of recipients in each of five race categories: Asian/Pacific Islander, Black, White, a combined group for other race, and unknown is shown.

Ethnicity
The percentage of Hispanic and non-Hispanic recipients is reported.

Age
Age was determined as of the date of transplant for each patient. The percentage of recipients in each of several age ranges is reported.

Gender
The percentage of male and female recipients is reported.

Previous Transplants
The percentage of recipients who previously received any organ transplant is shown.

Peak Panel Reactive Antibody (Kidney, Pancreas and Kidney/Pancreas Programs Only)
The recipients' highest panel reactive antibody (PRA) on the waitlist is shown for recipients who received a kidney, pancreas, or kidney/pancreas. The percentage of recipients in each of several PRA ranges (0-9, 10-79, 80+) is reported.

Body Mass Index
Body mass index is calculated at transplant as the recipient's weight divided by the height squared (BMI = Weight (kg)/ Height2 (m2)). The percentage of recipients in each of several BMI ranges (0-20, 21-25, 26-30, 31+) is reported.

Kidney

Glomerular diseases
Tubular and interstitial disease
Polycystic kidney disease
Congenital, familial, metabolic renal diseases
Diabetes mellitus
Renovascular & vascular diseases
Neoplasms
Hypertensive nephrosclerosis
Retransplant/graft failure
Other kidney diseases
Missing

Liver

Acute hepatic necrosis
Non-cholestatic cirrhosis
Cholestatic liver disease/cirrhosis
Biliary atresia
Metabolic diseases
Malignant neoplasms
Other
Missing

Intestine

Short gut syndrome
Functional bowel problem
Retransplant/graft failure
Other
Missing

Heart

Cardiomyopathy
Coronary artery disease
Retransplant/graft failure
Valvular heart disease
Congenital heart disease
Other
Missing

Lung

Congenital disease
Retransplant/graft failure
Primary pulmonary hypertension
Cystic fibrosis
Idiopathic pulmonary fibrosis
Alpha-1-antitrypsin deficiency
Emphysema/Chronic obstructive pulmonary disease (COPD)
Other
Missing

Heart-Lung

Congenital disease
Retransplant/graft failure
Primary pulmonary hypertension
Cystic fibrosis
Idiopathic pulmonary fibrosis
Alpha-1-antitrypsin deficiency
Emphysema/Chronic obstructive pulmonary disease (COPD)
Other
Missing

Recipient Medical Urgency Status at Waitlist (Liver and Heart Programs for Patients with Deceased Donors Only)
The recipients' medical urgency status when registered on the waitlist is shown for liver and heart programs. The percentage of recipients in each of status type (Livers: Status 1, 2A, 2B, 3, Temporarily Inactive; Hearts: Status 1, 1A, 1B, 2, Temporarily Inactive) is reported.

Recipient Medical Urgency Status at Transplant (Liver and Heart Programs for Patients with Deceased Donors Only)
The recipients' medical urgency status at the time of transplant is shown for liver and heart programs. The percentage of recipients in each of status type (Livers: Status 1, 2A, 2B, 3, Temporarily Inactive; Hearts: Status 1, 1A, 1B, 2, Temporarily Inactive) is reported.

Beginning on February 27, 2002 candidates for liver transplants were classified by MELD or PELD score rather than medical urgency status. However, Status 1 and "temporarily inactive" candidates were still grouped by their respective statuses. MELD and PELD scores were computed based on the candidates’ laboratory measures at the time of transplant. The following groups appear for liver recipients after February 27, 2002: Status 1, MELD 6-10, MELD 11-20, MELD 21-30, MELD 31-40, PELD 10 or less, PELD 11-20, PELD 21-30, PELD greater than 30, and Temporarily Inactive.

Recipient Medical Condition at Transplant
The medical condition of the recipient at transplant is shown. The percentage of recipients in each of 3 conditions (In ICU, Hospitalized, Not Hospitalized) is reported. The percentage without a condition reported is also shown.

Recipient Life Support Status at Transplant
The type of life support at transplant is shown for heart transplant recipients. Life support status is divided into three groups: no life support, devices (including ventricular assist devices (VAD), extracorporeal membrane oxygenation (ECMO), intraaortic balloon pump (IABP), and total artificial heart (TAH)), and other life support. The percentage without a status reported is also displayed.

Table 8. Summary for Characteristics of Transplant Donors

Table 8 summarizes the characteristics of living (kidney, liver and lung only) and deceased transplant donors who donated an organ between January 1, 2002 and December 31, 2002 in this center, with corresponding average values among donors in this center's OPTN region and the U.S. as a whole. Only donors whose organs were transplanted to recipients at this center, in this center's OPTN region, and the U.S. as a whole are counted.

Patient Count
The total number of organ donors whose donated organs were of the type corresponding to this center's program and that were transplanted during this period at this center is reported. The summaries of the donor characteristics in Table 8 are based on the patient population count.

Cause of Death
For deceased donors, the percentage of organs recovered and transplanted from donors in each of the major cause of death categories is reported. The categories for cause of death are Stroke, Motor Vehicle Accident (MVA), and Other.

Age
Donor age was determined as of the date of organ procurement for each donor. The percentage of donors in each of several age ranges is reported.

Race
The percentage of donors in each of five race categories: Asian/Pacific Islander, Black, White, a combined group for other race, and unknown, are shown.

Ethnicity
The percentage of Hispanic and non-Hispanic donors is reported.

Gender
The percentage of male and female donors is reported.

Blood Type
The percentage of donors by ABO type (O, A, B, AB) is reported. Donors with ABO type A, A1, or A2 were classified as A. Donors with ABO type AB, A1B, or A2B were classified as AB.

Expanded Criteria Donors
The percentage of donors (for kidney programs only) by whether or not they met the expanded donor criteria is reported. Donors that meet the expanded criteria are those over 60 years of age and those between 50 and 59 years of age who either died of a stroke, had a history of hypertension, or had a serum creatinine of greater than 1.5.

Table 9. Summary for Characteristics of Transplant Operations

Table 9 summarizes the characteristics of cadaveric transplants performed between January 1, 2002 and December 31, 2002 at this center, with corresponding average values for transplants performed in this center's OPTN region and the U.S. as a whole. For kidney, liver and lung programs, a comparable table summarizing characteristics of living donor transplant operations is also provided.

Patient Count
The total numbers of cadaveric transplants during this period at this center, in this center's OPTN region, and the U.S. as a whole are reported. For kidney and liver programs, the total number of living donor transplants during this period at this center, in this center's OPTN region, and the U.S. as a whole are reported. The summaries of the transplant characteristics in Table 9 are based on the patient population count.

Cold Ischemic Time (Deceased Donor Transplants Only)
The percent of transplants that fall into each category of cold ischemic time are reported by whether the donated organ was procured locally or from outside the OPO (see Sharing below). This time is divided into 90-minute increments for thoracic transplants, and by ranges of hours for the other organs.

Relation With Donor (Living Donor Transplants Only)
The percent of transplants whose living donor was biologically related (Related) or biologically unrelated (Unrelated) are reported.

Level of Mismatch
Level of HLA mismatch (0-6) is calculated by comparing antigen values for the A, B and DR loci between donors and their respective recipients, accounting for known antigen splits. The number of mismatches is derived by subtracting the number of matches and missing donor values from the number of potential matches (six).

Procedure Type
The procedure type, meaning whether the organ was transplanted alone or with other organs, is shown. For kidney/pancreas programs, organs in addition to a kidney and pancreas are included in the 'Multi-Organ' column.

Dialysis in First Week After Transplant
The percentage of patients who received dialysis treatment within one week following transplant is shown. This is only shown for kidney recipients.

Sharing (Deceased Donor Transplants Only)
Shown are the percent of transplants for which the organ was procured outside the center's OPO (shared) and the percent of transplants where the organs were procured from within the center's OPO (local).

Median Length of Stay
Shown is the actual number of days the patient remained in the hospital following receipt of a transplant. If a patient receives multiple transplant of the same organ during the same hospital stay, the number of days is from the first transplant until the final discharge date. Multiple organ transplants are excluded from this statistic in most cases. The kidney-pancreas and heart-lung tables include only kidney-pancreas or heart-lung transplants, but not other multi-organ transplants.

Table 10. Graft Survival Rates

Table 10 reports graft survival (the fraction of grafts that are still functioning) at several time points after transplantation. Graft survival is reported at the 1-month, 1-year, and 3-year reporting time points for each center, with corresponding rates for the U.S. Only those transplants that accrued between January 1, 1998 and June 30, 2002 were eligible for inclusion in the analyses. For the 1-month and 1-year statistics for non-thoracic organs, transplants accrued between January 1, 2000 and June 30, 2002 were included. Transplants that occur during the last 6 months of this cohort have only 6 months of follow-up available but can be included using censored data methods (described below) in the 1-year statistics. For the 1-month and 1-year statistics for thoracic organs, only transplants accrued between January 1, 2000 and December 31, 2001 were included. The first follow-up time point for these organs is at 1 year so they would not contribute any information to either the 1-month or the 1-year statistics. For the 3-year survival statistics, transplants accrued between January 1, 1998 and December 31, 1999 were included.

Statistics are generally reported separately for adult (age 18 and older) and pediatric (age less than 18) patients. For lungs, statistics are reported instead for patients 12 and older and for children less than 12. In addition, statistics are reported separately by donor type (cadaveric and living) for kidney and liver programs. There are some organs or subgroups of patients for which there are too few transplants or too few events to calculate meaningful statistics. The table below indicates which statistics are calculated for each organ.

Not all transplant recipients had complete graft survival through the end of the time interval since transplant. However, all available follow-up data for each graft were used in the calculation of the statistics reported here using standard censored data methods of survival analysis (Cox 1972, Kaplan-Meier 1958). Additional data from the Social Security Death Master File (SSDMF) have been incorporated into the graft survival rates. If the SSDMF data report that a patient died before the last OPTN follow-up date, this date is used as the graft failure date. Since follow-up for graft survival is censored at the last OPTN follow-up date, SSDMF deaths alive. after this date are not included in the analyses.

Exceptions: Transplants with a graft failure date recorded as having occurred prior to the transplant and transplants with no follow-up forms, missing last follow-up date or last follow-up date before the transplant were analyzed as censored (lost to follow-up) on the day of transplant. This means they do not affect the reported results and they are included only to retain consistency with the reported number of transplants. Transplants with no follow-up forms will influence the statistics related to completeness of data (described elsewhere).

Statistics Reported in Graft Survival Table (Table 10) by Organ

	Counts of Transplants and Actual¹ Graft Survival		Expected² Graft Survival
ORGAN	Adult	Pediatric	Adult	Pediatric
Heart	Yes	Yes	Yes	Yes
Heart-Lung	Yes	No	No	No
Lung	Yes	Yes	Yes	No
Liver	Yes	Yes	Yes	Yes
Kidney	Yes	Yes	Yes	Yes
Intestine	Yes	Yes	No	No
Pancreas	Yes	No	No	No
Kidney-Pancreas	Yes	No	Yes	No

¹ Graft survival is the actual graft survival for those programs with complete data and was estimated using the Kaplan-Meier methodology at those centers with incomplete follow-up reporting. ² Expected graft survival is based on data from the entire nation to evaluate the survival expected for the patients at each center, based upon their characteristics.

Number of Transplants
The total number of transplants reported during the accrual periods for the 1-month, 1-year and 3-year graft survival analyses are shown for each patient age cohort. The 1-month and 1-year counts are the same since the accrued periods are the same.

Living donor transplants are included only for kidneys and livers. With some exceptions, the tables include only single-organ transplants. The intestine tables include both single-organ intestine transplants and liver-intestine transplants. The kidney-pancreas and heart-lung tables include only kidney-pancreas or heart-lung transplants, but not other multi-organ transplants. Heterotopic heart and liver transplants are not included.

Graft Survival
A graft is counted as failed when follow-up information indicates that one of the following has occurred prior to the reporting time point: graft failure, retransplant, death, or dialysis treatment has been resumed (for kidney only). OPTN follow-up forms are used to identify these events. The SSDMF is used in conjunction with OPTN data to identify deaths.

Transplants that occurred in the last six months of the accrual period for the 1-year reporting time point are only followed for six months after transplant because the 1-year follow-up information is not yet available in the current OPTN data. The reporting time point for this subset of transplants is six months after transplantation.

The follow-up time for each graft (days at risk) is the number of days from transplantation until graft failure (as defined above), last known follow-up date, or the reporting time point (e.g., 1 month, 1 year, or 3 years) occurs, whichever is earliest. Grafts that were known to be functioning at their last reported follow-up time were analyzed as censored if that time was before the reporting time point. The actual graft survival status at the reporting time point is not known for censored patients.

The "Graft Survival" at 1 month, 1 year and 3 years was calculated from the follow-up data using the Kaplan-Meier (KM) method and is an estimate for the fraction of all grafts that would still be functioning at the reporting time point had they been followed to that time. The KM method uses all data, including the incomplete data for patients who were lost before the end of the period. The KM method assumes that the failure rate would be the same for those patients lost to follow-up as was observed for those with complete data.

After a patient was recorded as lost to follow-up on one follow-up record, any subsequent follow-up records were disregarded. These calculations do not include any deaths that occur after loss to follow-up in the OPTN database, because date of graft failure if unknown and may have occurred before the death.

Expected Graft Survival
The "Expected Graft Survival" is the fraction of grafts that would be expected to be functioning at each reported time point, based on the national experience for patients similar to those at this center. The "Graft Survival" can be compared to the "Expected Graft Survival" as the percent of grafts functioning at the reporting time points. If the "Graft Survival" is greater than the "Expected Graft Survival", then the graft survival is better at this center than would be expected based on the national transplant experience for similar grafts and patients.

The national experience was analyzed using data for all grafts at all facilities in the United States. A Cox proportional hazards regression model for time to graft failure (Cox 1972) was fitted to the national data, which yielded the probability of graft failure for each patient, based upon the characteristics of each patient and the reporting time point. The characteristics accounted for in these calculations are reported below and are similar to those that have been used in previous reports. The "Expected Graft Survival" for each organ was adjusted for the patient characteristics as listed in the Model Description Tables. See Section XII for details on the calculation of the expected graft survival.

Ratio of Observed to Expected Graft Failures
For statistical comparisons, it is appropriate to compare the number of graft failures observed during follow-up (which is shorter than the reporting time point for censored patients) to the number of graft failures that would be expected during follow-up, rather than by comparison of observed and expected survival rates at the reporting time points. The ratio of observed to expected graft failures compares the entire survival curve up to the reporting time point to the curve expected for patients with the same characteristics based on the national experience rather than just the survival at the reporting time point. A ratio greater than 1.00 indicates that there were more graft failures at the center than would have been expected based on the national experience, while a ratio less than 1.00 indicates that there were fewer graft failures at the center than would have been expected based on the national experience. For example, a ratio of 1.20 indicates that the graft failure rate at the center was, on average, 20% higher than the national rate. A ratio equal to 1.00 indicates that the graft failure rates at the center are the same as the national graft failure rates.

Random variation
The ratio reported is an estimate of the true ratio of graft failure rates at the center relative to the national graft failure rates. A ratio different from 1.00 indicates that the true graft failure rates at the center differ from the national graft failure rates. However, the value of the ratio varies from year to year above and below the true ratio due to random variation. Thus, the ratio could differ from 1.00 due to random variation, rather than due to a true difference between the andgraft failure rates at the center and in the nation. Both the p-value and the confidence interval, discussed below, are designed to help in the interpretation of the ratio in the face of such random fluctuations.

95% Confidence Interval
The 95% confidence interval for the ratio of observed to expected graft failures gives a range of plausible values for the true ratio of center to national graft failure rates, in light of the observed ratio The true ratio lies within this range 95% of the time. The confidence interval is a measure of how precisely we are able to estimate the ratio. If the 95% confidence interval includes 1.00, then the ratio is not significantly different than 1.00, which means that the graft failure rates at the center are not significantly different than the national rates (p<0.05).

P-value
The p-value measures the statistical significance (or evidence) for testing the (two-sided) hypothesis that the true ratio of graft failure rates for the center versus the nation equals 1.00. A smaller p-value tends to occur when the ratio differs more greatly from 1.00 and when more patient data are used to calculate the ratio. A p-value less than 0.05 is often taken as evidence that the ratio of graft failure rates truly differs from 1.00. Thus, a p-value less than 0.05 indicates that the difference between the graft failure rates at the center and the nation is unlikely to have arisen from random fluctuations alone. The smaller the p-value, the more statistically significant is the difference between the national and the center graft failure rates. A small p-value helps to rule out the possibility that the difference of the ratio from 1.00 could have arisen by chance. However, a small p-value does not indicate whether or not the magnitude of the difference between the death rates at the center and the nation is important. The actual quantitative value of the ratio reflects the clinical importance of the difference between the center and national graft failure rates. A ratio that differs greatly from 1.00 is more important while a ratio in the range 0.95 to 1.05 is not as important.

The p-value was calculated by testing whether the observed number of graft failures was statistically greater or less than the expected number of graft failures at a center, based on the Poisson distribution for the observed number of graft failures. The p-value is not shown if the expected graft survival was not calculated.

How do the rates at this center compare to those in the nation?
This line indicates whether the actual graft survival is statistically different than the expected graft survival based on the p-value on the previous line. If the p-value is less than or equal 0.05 then this line reads "Statistically Higher" or "Statistically Lower" depending on whether the actual graft survival is higher or lower than the expected graft survival. "Statistically Higher" survival corresponds to better outcomes (ratios less than 1.00), while "Statistically Lower" survival corresponds to worse outcomes (ratios greater than 1.00). If the p-value is greater than 0.05 then this line reads "Not Significantly Different". This value is not shown if the expected graft survival is not calculated.

Follow-Up Days Reported
This line reports the percentage of days that are targeted for inclusion during the follow-up period relative to the number of days that were actually reported with follow-up forms. For grafts that did not fail before the end of the period, the targeted number of days of follow-up is the entire period (30, 365 or 1096 days; see next section for details on maximum follow-up). For non-thoracic grafts transplanted during the last 6 months of the period, the targeted follow-up for 1 year survival is 6 months. For grafts that failed before the end of the period, the number of targeted days of follow-up is the number of days until graft failure. The number of days of reported follow-up is less than the targeted number of days for censored patients. Examples are shown in the table below. The total number of days of follow-up reported for all patients are summed and divided by the total number of days of follow-up targeted to obtain the percent reported in this line.

Patients with incomplete follow-up are included in the analyses until the date of the last reported follow-up. The presence of incomplete, or censored, data reduces the precision and interpretability of the statistics reported here. A low percent may indicate a non-random sample from this center for follow-up. Examples of incomplete follow-up and the calculation of the percent of follow-up reported are shown in the table below.

Examples of incomplete follow-up and calculations of follow-up days reported

Transplant Date	Last Report	Reporting Time Point	Follow-Up Time	Graft Status	Follow-Up Reported (%)

7/1/98	3/1/99	30 days	30 days	Functioning	100%
7/1/98	3/1/99	1 year (365 days)	244 days	Functioning (Pt Censored)	67%
7/1/96	7/1/97	3 years (1096 days)	367 days	Failed Dead	100%
7/1/96	7/1/97	3 years (1096 days)	367 days	Functioning (Pt Censored)	35%

If this percentage is low, then the graft survival reported is not a reliable estimate of the true graft survival for the time period.

Maximum Days of Follow-Up
Patients were followed for up to 30 days for the 1-month statistics, up to 365 days for the 1-year statistics and up to 1096 days for the 3-year statistics starting at the day of transplant (day 1). The maximum follow-up time for patients in the center is reported on this line. If this maximum is less than 30 days for the 1-month, 365 for the 1-year or 1096 for the 3-year statistics, then the graft survival reported is not a reliable estimate of the true graft survival for the time period.

Table 11. Patient Survival Rates

Table 11 reports patient survival (the fraction of patients that are still alive) at several time points after first transplantation for this organ. Patient survival is reported at the 1-month, 1-year, and 3-year reporting time points for each center, with corresponding rates for the U.S. Only those transplants that accrued between January 1, 1998 and June 30, 2002 were eligible for inclusion in the analyses. For the 1-month and 1-year statistics for non-thoracic organs, transplants accrued between January 1, 2000 and June 30, 2002 were included. Transplants which occur during the last 6 months of this cohort have only 6 months of follow-up available but can be included using censored data methods (described below) in the 1-year statistics. For the 1-month and 1-year statistics for thoracic organs, only transplants accrued between January 1, 2000 and December 31, 2001 were included. The first follow-up time point for these organs is at 1 year so they would not contribute any information to either the 1-month or the 1-year statistics. For the 3-year survival statistics, transplants accrued between January 1, 1998 and December 31, 1999 were included. Table 11 includes all patients who received their first transplant of this organ type during the accrual period. Patients who had previously received a transplant of this type, whether this previous transplant occurred during the accrual period or not, were not included. For this reason, the patient count in Table 11 may be smaller than the transplant count in Table 10.

Statistics are generally reported separately for adult (age 18 and older) and pediatric (age less than 18) patients. For lungs, statistics are reported instead for patients 12 and older and for children less than 12. In addition, statistics are reported separately by donor type (cadaveric and living) for kidney and liver programs. There are some organs or subgroups of patients for which there were too few transplants or too few events to calculate meaningful statistics. The table below indicates which statistics are calculated for each organ.

Additional data from the Social Security Death Master File (SSDMF) have been incorporated into the patient survival rates. The SSDMF data are used in conjunction with OPTN data to determine whether each patient is alive at the end of the follow-up period. If the patient is not reported to have died in either source, the patient is assumed to be alive.

Statistics Reported in Patient Survival Table (Table 11) by Organ

	Counts of Transplants and Actual¹ Patient Survival		Expected² Patient Survival
ORGAN	Adult	Pediatric	Adult	Pediatric
Heart	Yes	Yes	Yes	Yes
Heart-Lung	Yes	No	No	No
Lung	Yes	Yes	Yes	Yes
Liver	Yes	Yes	Yes	Yes
Kidney	Yes	Yes	Yes	No
Intestine	Yes	Yes	No	No
Pancreas	Yes	No	No	No
Kidney-Pancreas	Yes	No	Yes	No

¹ Patient survival is the actual patient survival for those centers with complete data and was estimated using the Kaplan-Meier methodology at those centers with incomplete follow-up reporting. ² Expected patients survival is based on data from the entire nation to evaluate the survival expected for patients at each center, based upon their characteristics.

Number of Patients
The total number of patients reported to have received their first transplant of the organ type during the accrual periods for the 1-month, 1-year and 3-year patient survival analyses are shown for each patient age cohort. The 1-month and 1-year counts are the same since the accrued periods are the same. Note that this line reports counts of patients rather than transplants and therefore will not be the same as the count of transplants in Table 10.

Patients receiving living donor transplants are included only for kidneys and livers. With some exceptions, the tables include only patients receiving single-organ transplants. The intestine tables include both patients receiving either single-organ intestine transplants or liver-intestine transplants. The kidney-pancreas and heart-lung tables include only patients receiving kidney-pancreas or heart-lung transplants, but not other multi-organ transplants. Patients receiving heterotopic heart and liver transplants are not included.

Patient Survival
A patient is counted as having died when follow-up information or SSDMF data indicates that a death has occurred prior to the reporting time point.

Patients who are transplanted in the last six months of the accrual period for the 1-year reporting time point are only followed for six months after transplant because the 1-year follow-up information is not yet available in the current OPTN data. The reporting time point for this subset of patients is six months after transplantation.

The follow-up time for each patient (days at risk) is the number of days from transplantation until death or the reporting time point (e.g., 1 month, 1 year, or 3 years) occurs, whichever is earliest. The "Patient Survival" at 1 month, 1 year and 3 years was calculated from the OPTN follow-up data and SSDMF data using the Kaplan-Meier (KM) method. It is an estimate for the fraction of all accrued patients who would still be alive at the reporting time point had they been followed to that time.

Expected Patient Survival
The "Expected Patient Survival" is the fraction of patients who would be expected to be alive at each reported time point, based on the national experience for patients similar to those at this center. The "Patient Survival" can be compared to the "Expected Patient Survival" as the percent alive at the reporting time points. If the "Patient Survival" is greater than the "Expected Patient Survival", then the patient survival is better at this center than would be expected based on the national transplant experience for similar patients.

The national experience was analyzed using data for all accrued transplants at all facilities in the United States. A Cox proportional hazards regression model for time to death (Cox 1972) was fitted to the national data, which yielded the probability of survival to the reporting time point for each patient, based upon the characteristics of each patient and the reporting time point. The expected survival is the average of these computed probabilities. The characteristics accounted for in these calculations are reported below and are similar to those that have been used in previous reports. The "Expected Patient Survival" for each organ was adjusted for the patient characteristics as listed in the Model Description Tables. See Section XII for details on the calculation of the expected patient survival.

Ratio of Observed to Expected Deaths
For statistical comparisons, it is appropriate to compare the number of deaths observed during follow-up (which is shorter than the reporting time point for censored patients) to the number of deaths that would be expected during follow-up, rather than by comparison of observed and expected survival rates at the reporting time points. The ratio of observed to expected deaths compares the entire survival curve up to the reporting time point to the curve expected for patients with the same characteristics based on the national experience rather than just the survival at the reporting time point. A ratio greater than 1.00 indicates that there were more deaths at the center than would have been expected based on the national experience, while a ratio less than 1.00 indicates that there were fewer deaths at the center than would have been expected based on the national experience. For example, a ratio of 1.20 indicates that the death rate at the center was, on average, 20% higher than the national rate. A ratio equal to 1.00 indicates that the death rates at the center are the same as the national death rates.

Random variation
The ratio reported is an estimate of the true ratio of death rates at the center relative to the national death rates. A ratio different from 1.00 indicates that the true death rates at the center differ from the national death rates. However, the value of the ratio varies from year to year above and below the true ratio due to random variation. Thus, the ratio could differ from 1.00 due to random variation, rather than due to a true difference between the death rates at the center and in the nation. Both the p-value and the confidence interval, discussed below, are designed to help in the interpretation of the ratio in the face of such random fluctuations.

95% Confidence Interval
The 95% confidence interval for the ratio of observed ot expected deaths gives a range of plausible values for the true ratio of center to national death rates, in light of the observed ratio The true ratio lies within this range 95% of the time. The confidence interval is a measure of how precisely we are able to estimate the ratio. If the 95% confidence interval includes 1.00, then the ratio is not significantly different than 1.00, which means that the death rates at the center are not significantly different than the national rates (p<0.05).

P-value
The p-value measures the statistical significance (or evidence) for testing the (two-sided) hypothesis that the true ratio of death rates for the center versus the nation equals 1.00. A smaller p-value tends to occur when the ratio differs more greatly from 1.00 and when more patient data are used to calculate the ratio. A p-value less than 0.05 is often taken as evidence that the ratio of death rates truly differs from 1.00. Thus, a p-value less than 0.05 indicates that the difference between the death rates at the center and the nation is unlikely to have arisen from random fluctuations alone. The smaller the p-value, the more statistically significant is the difference between the national and the center death rates. A small p-value helps to rule out the possibility that the difference of the ratio from 1.00 could have arisen by chance. However, a small p-value does not indicate whether or not the magnitude of the difference between the death rates at the center and the nation is important. The actual quantitative value of the ratio reflects the clinical importance of the difference between the center and national death rates. A ratio that differs greatly from 1.00 is more important while a ratio in the range 0.95 to 1.05 is not as important.

The p-value was calculated by testing whether the observed number of deaths was statistically greater or less than the expected number of deaths at a center, based on the Poisson distribution for the observed number of deaths. The p-value is not shown if the expected graft survival was not calculated.

How do the rates at this center compare to those in the nation?
This line indicates whether the actual patient survival is statistically different than the expected patient survival based on the p-value on the previous line. If the p-value is less than or equal 0.05 then this line reads "Statistically Higher" or "Statistically Lower" depending on whether the actual patient survival is higher or lower than the expected patient survival. "Statistically Higher" survival corresponds to better outcomes, while "Statistically Lower" survival corresponds to worse outcomes. If the p-value is greater than 0.05 then this line reads "Not Significantly Different". This value is not shown if the expected patient survival is not calculated.

Follow-Up Days Reported
This line reports the percentage of days that are targeted for inclusion during the follow-up period relative to the number of days that were actually reported with follow-up forms. For patients who did not die before the end of the period, the targeted number of days of follow-up is the entire period (30, 365, or 1096 days; see next section for details on maximum follow-up). For patients who died before the end of the period, the number of targeted days of follow-up is the number of days until death. With the inclusion of SSDMF data, the number of days of reported follow-up is always equal to the targeted number of days for all patients regardless of death. Because of this, the percent of follow-up days is always equal to 100%. However, the number of follow-up days reported in this row is based on OPTN data only since there would be no difference between centers otherwise. Even with the inclusion of SSDMF data, a low percent may indicate under-ascertainment of mortality for a given facility since the completeness of follow-up data is still partially determined by center reporting.

Maximum Days of Follow-up
Patients were followed for up to 30 days for the 1-month statistics, up to 365 days for the 1-year statistics and up to 1096 days for the 3-year statistics starting at the day of transplant (day 1). The maximum follow-up time for patients in the center is reported on this line. If this maximum is less than 30 days for the 1-month, 365 for the 1-year or 1096 for the 3-year statistics, then the patient survival reported is not a reliable estimate of the true patient survival for the time period.

Technical Notes on Computing Expected Patient or Graft Survival

Model Fitting Methods
Survival models are adjusted for patient characteristics. The model used for each organ is adjusted for patient characteristics specific to that organ, so we refer to the list of characteristics generically with the notation x. Individual patients are numbered sequentially and we refer generically to the i^th patient. The specific values of the characteristics for patient i are denoted by x_i. Based on a model, we calculate S_i(t), the probability of survival to time t for patients with characteristics x_i. The probability of survival at time point t₀ for patient i is S_i(t₀). The average survival for the n accrued transplant patients at the center is calculated as (1/n) S_i(t₀) (Zucker). The expected number of events during follow-up for each patient was calculated as -ln(S_i(t_i)) where S_i(t_i) is the survival curve adjusted to the characteristics of patient i, and t_i is the follow-up time for that patient up to time t₀(SAS/STAT User's Guide, Andersen, Collett). The expected number of events is - ln(S_i(t_i)) for the n transplants during the follow-up times for the patients at this center.

The models included patient characteristics determined to be important in this and previous Center-Specific Reports (UNOS October 2000). In addition, if one level of a characteristic was included, the others were also included. For example, if black recipient was included in a model in the past, then the current model included each of the race groups. Also, if an interaction was included in previous reports, then the main effects for that interaction were also included.

The Model Description Tables indicate the value of the coefficient for each characteristic in each of the models (beta) as well as the corresponding standard error and a p-value indicating if the coefficient is significantly different than 0. The relative risk (RR) for mortality or graft loss associated with a particular patient characteristic, compared to the reference group for that characteristic, can be calculated as RR=exp(beta). For continuous variables, this is interpreted as the RR associated with 1 unit higher value (e.g. for ischemia time, it would be the RR associated with 1 hour longer time). However, keep in mind that these models are estimated for the purposes of adjustment, not for interpretation of coefficients. Some standard errors are large, which reflects uncertainty in the interpretation of the corresponding covariate, but does not adversely affect the accuracy of the adjusted estimate. For example, coefficients that are more negative than -7 can occur when there are no events in the corresponding group of patients.

Missing Data
In general, patients with missing values for variables entered into the model as categorical variables were included in their own category or in the reference group. Missing values for variables entered into the model as continuous values were replaced with the mean value (these mean values are included as footnotes in the model description tables). In some cases there is also a categorical variable indicating whether the value was missing. Note that characteristics such as age are included in some models as categorical variables and in others as continuous variables.

The model description tables list all the covariates included in each model and indicates (indirectly) how missing values were handled in each particular case. Looking at the variables corresponding to a particular characteristic or value in a model will indicate whether missing values are included in a category. If there is no category that includes the missing values, patients with missing values are included with the reference group. For continuous values, there may be a category for those with missing values, but patients with missing values are also assigned a value for the continuous variable itself. For most variables, missing values are replaced with the mean. For HLA mismatch, missing values are replaced with 3.5. The mean values needed are listed in the footnotes for each model description table.

Notes on Diagnosis, Ischemia Time, and Other Continuous Variables

Adjusting for Diagnosis
In models adjusting for diagnosis, the diagnosis groups and reference groups differ by organ and in some cases by age group.

Kidney - 8 groups for adult models, 9 for pediatric models:

glomerular diseases* (reference group for adult models)
diabetes
hypertensive nephrosclerosis
polycystic kidney disease
tubular and interstitial diseases
renovascular and other vascular diseases
congenital, familial, and metabolic kidney diseases (ref. for pediatric models)
other/missing

* For the pediatric models, this group was broken into two groups:

focal segmental glomerulosclerosis (FSG)
other glomerular diseases

Liver - 6 groups for adult models, 7 for pediatric models:

cholestatic liver disease/cirrhosis
non-cholestatic cirrhosis (reference for adult models)
acute hepatic necrosis (AHN)
metabolic disease
malignancy
other/missing
For pediatric models only: biliary atresia (reference for pediatric models)

Lung Models by Diagnosis
For lungs, there are separate models for each of 4 diagnosis groups. These diagnosis groups are:

COPD/Emphysema and alpha-1-antitrypsin deficiency
Primary pulmonary hypertension and Eisenmenger's
Cystic fibrosis
Idiopathic pulmonary fibrosis

Any diagnosis that could not be included with one of these four groups was included with the idiopathic pulmonary fibrosis group. This group is therefore labeled "Idiopathic pulmonary fibrosis and not classified" in the model description tables. This grouping system was developed by the OPTN Thoracic Committee (as of November 2002). A complete mapping of diagnoses is available from the SRTR.

Ischemia Time and Other Continuous Variables
Ischemia time refers to cold ischemia time for kidney and liver transplants, total time for heart transplants and maximum time for lung transplants. In all models, ischemia time was measured in hours. Ischemia time was generally included in the models as both a linear and a quadratic term as well as an indicator for missing ischemia time. Ischemia time was centered on the average ischemia time by organ and missing values were set to the mean as described in the previous section. The mean values for each organ are included as footnotes in the corresponding model description tables.

Other instances in which continuous variables are included in the models are treated similarly. The continuous term is centered on the mean and missing values are set equal to the mean as described in the previous section.

Calculation of Individual Expected Survival
The tables of coefficients can be used to calculate the expected graft or patient survival at 1 month, 1 year, and 3 years for a specific patient.

Suppose that p is the number of patient characteristics listed in the appropriate model table and x_ij is the specific value of the j^th characteristic for the i^th patient. For patient i, we calculate

X_i'ß = ß₁x_i1 + ß₂x_i2+ ... + ß_px_ip

where b_j is the j^th coefficient from the model.

For a categorical characteristic, the value is 1 if the patient falls into the category and 0 otherwise. For linear ischemia time, subtract the average ischemia time (given above) from the patient's ischemia time (in hours) before multiplying by the corresponding ß_i. For quadratic ischemia time, subtract the average ischemia time (given above) from the patient's ischemia time (in hours) and square it before multiplying by the corresponding ß_i. For HLA mismatch values 1-6, subtract 3.5 from the patient's HLA mismatch value before multiplying by the corresponding ß_i.

The Cox model yields estimates of the coefficients ß_j and the baseline survival curve, S₀(t). For patient i, with characteristics

x_i = x_i1, x_i2, ... , x_ip

we calculate

S_i(t₀) = [S₀(t₀)]^exp(x_i'ß) ,

the expected survival at time point t₀ (t₀ = 1 month, 1 year, or 3 years).

Then

S_Avg(t₀) = (1/N) S_i(t₀)

is the expected survival at time t₀ for this facility.

We also calculate

S_i(t_i) = [S₀(t_i)]^exp(x_i'ß)

Then -ln(S_i(t_i)) is equal to the expected number of events for patient i during follow-up and

-ln[S_i(t_i)]

is the expected number of events during follow-up at the facility.

NOTATION:

N = number of transplants accrued
t₀ = reporting time point (e.g. 1 month, 1 year, 3 years)
t_i = end of follow-up for patient i during period. Note t_i < t₀ for patients who die or are lost to follow-up during the period.
S_i(t₀) = fraction surviving to end of period adjusted to characteristics of patient i
S_Avg(t₀) = expected fraction surviving to end of period adjusted to average characteristics of patients at the facility

References

Andersen PK, Borgun O, Gill RD, Keiding N. Statistical Models Based on Counting Processes. Springer-Verlag, New York. 1993. See pages 334 and 406-407.

Breslow NE, Day NE. Statistical methods in cancer research (Volume II), IARC, Lyon, 1987.

Colett D, Modeling Survival Data in Medical Research. Chapman and Hall, London, 1994. See page 153 equation 5.6 and page 151, equation 5.1.

Cox DR. Regression Models and life tables (with discussion). J R Stat Soc 1972; 34: 197-220.

Kaplan EL, Meier P. Nonparametric estimation from incomplete observations. J. Am. Stat. Assoc. 1972; 53:457-481.

SAS Institute Inc., Ref SAS/STAT User's Guide, Version 8, Cary, North Carolina: SAS Institute Incorporated, 1999, p 2598-99.

Zucker DM. Restricted mean life with covariates: modification and extension of a useful survival analysis method. J. Amer. Statist. Assoc. 1998; 93:702-709.