Transplant Statistics: Annual Report

Technical Notes and Analytic Methods
Registrations and Time to Transplant

The "Time to Transplant" tables take a cohort of new waiting list registrations in a calendar year and show how long it takes for 10%, 25%, and 50% (the median) of those patients to be transplanted, whether from a cadaveric or living donor. These tables take the point of view of a patient who has just been registered on a waiting list and who wants to know his or her prospects for receiving a transplant. These tables take into account all of the things that can happen after listing, including receiving a transplant, being removed from the waiting list, and dying. For instance, for an 18-34 year old transplant candidate being added to the kidney waiting list in 2000, the 10th percentile of time to transplant is 57 days, the 25th percentile is 191 days, and the median is 530 days, This means that there is a 10 % chance that the candidate will receive a transplant in the first 57 days, a 25% chance in the first 191 days, and a 50% chance in the first 530 days after registration. (Klein)

The "Time to Transplant" tables show registrations and percentiles of time to transplant (in days) for patients awaiting transplantation, categorized by certain demographic and medical factors. The number of registrations and the 10th, 25th, and 50th (median) percentile times to transplant are shown. Each table also provides upper and lower confidence limits (statistical measures of precision) for the median time to transplant. Table 1.5 shows overall registrations and time to transplant for all organs by year. Kidney-pancreas waiting list data are reported starting in 1992, the year the kidney-pancreas waiting list was established. Intestine waiting list data are reported starting in 1993, the year the intestine waiting list was established. Organ-specific tables are presented in Table 2 of each of the organ-specific sections.

• Index 6.2     Kidney Time to Transplant
• Index 7.2     Pancreas Time to Transplant
• Index 8.2     Kidney-Pancreas Time to Transplant
• Index 9.2     Liver Time to Transplant
• Index 10.2   Intestine Time to Transplant
• Index 11.2   Heart Time to Transplant
• Index 12.2   Lung Time to Transplant
• Index 13.2   Heart-Lung Time to Transplant

The most recent year in the "Time to Transplant" tables may show the symbol "+" for the median time to transplant. This is because there has not been sufficient time for 50% of the patients to have been transplanted (see Table 2.1 for an example in which we are unable to compute the median time to transplant). For heart-lung and intestine transplants, median time to transplant cannot be determined for most of the one-year registrant cohorts. This can occur if mortality is so high for a given cohort that more than 50% of the registrants may have died before 50% have been transplanted.

The data reported are drawn from the OPTN waiting list and removal files. The OPTN members have direct responsibility for submitting, maintaining, and monitoring the data from the time their patients are listed until those patients are removed from the waiting list. Data are subject to change based on future data submission or correction.

The time to transplant is computed for annual cohorts based on the year of entry onto the waiting list. The value N in each table, for each year, represents the size of each cohort (i.e., the number of new organ-specific registrations entered during that year). Note that some patients are listed at different centers for the same organ type or for multiple organs (e.g., kidney and pancreas). The data in these tables are not adjusted for multiple listings. Therefore, each cohort consists of patient registrations rather than patients. Time to transplant for each registration is defined as the time (in days) after a candidate is placed on the waiting list, by which the corresponding percentage of all patients initially waitlisted had been removed from the waiting list for receiving a transplant. A Kaplan-Meier model was used with censoring on a) August 1, 2001 (the date on which the analysis was run) for those registrations still waiting on that date; and b) the date of removal from the waiting list for recovery.

For completeness, all categories of demographic and medical factors were listed in the tables, including those with no transplants in the cohort (N=0). In categories that had fewer than 10 patients in the cohort, time to transplant was not calculated and the symbol "*" appears. The "+" symbol indicates that the statistic was not calculated because of insufficient follow-up time for 50% of the cohort to be transplanted.

The time to transplant and confidence limit calculations, performed at the 95% confidence level, were computed using the statistical procedure PHREG in version 8.0 of SAS (SAS Institute). Using PHREG, the time to transplant estimates and median confidence limits were calculated from time to event curves estimated using the Kaplan-Meier method (Kaplan).