A Guide to Reading and Understanding the Center-Specific Reports (CSRs) Prepared by the Scientific Registry of Transplant Recipients (SRTR)

Overview:

These Center-Specific Reports contain a wide range of useful information about transplant programs operating in the United States. The information includes many features of the transplant program, such as the number of transplants performed in recent years, waiting time and waiting list outcomes, and post-transplant experience of patients served by this center. The statistics are arranged to allow comparisons to national averages, as well as to the experience for similar patients at other centers in the country. This report is based largely on data submitted by this transplant center for patients on the waiting list and those transplanted within the last five years.

Table 1 provides a picture of the volume and type of waiting list and transplant activity at this center. Nebraska Health System had 122 patients on its waiting list on 01/01/2001 and 115 patients on 12/31/2002. During these two years, 312 patients were added to the list and 319 patients were removed. Of the removals, 15 were for transplant from a living donor and 191 were for transplant from a deceased donor. Nebraska Health System performed 101 liver transplants (Table 7) during the last year (01/01/2002-12/31/2002). Typical liver programs currently operating in the United States transplanted between 14 and 62 people in that same period. More about the activity at this center and the types of patients served is found in the Table Details section below and in Tables 1 and 2 (waiting list) and Tables 7, 8, and 9 (transplant).

The likelihood of receiving a liver transplant differs from from facility to facility and also from person to person depending upon the medical condition of the candidate. Overall, at Nebraska Health System, 38.9 percent of patients placed on the waiting list had received a transplant by 6 months after listing, compared with 24.5 in the nation (Table 4). At 6 months, 10.5 percent had died (compared to 8.9 nationally) and 46.3 were still on the waiting list (61.4 nationally). These numbers are strongly influenced by the proportion of patients who are listed at a high medical urgency status. At this center, 20 of 162 of these patients were listed at Status 1. For these most urgent patients, 65.0 percent had received a transplant by 6 months after listing, compared with 56.0 in the nation (Table 4A). At 6 months, 25.0 percent had died (13.7 nationally) and 0.0 were still on the waiting list (9.1 nationally).

Other measures of waiting list outcomes are discussed below and shown in Tables 3 - 6.

At Nebraska Health System, 85.02 percent of patients were alive one year after transplant, compared to the 87.40 percent that would be expected based on the characteristics of these patients. However, the p-value of 0.499 indicates that there is a good chance (about 49.9 percent) that the difference between these rates is due to random chance. Similar comparisons may be made for shorter- (1 month) and longer-term (3 year) survival, also in Table 11, as well as for graft survival (Table 10). Further discussion of actual, expected, and national survival rates may be found in the Table Details section below.

Specific circumstances at each center may affect many of the measures reported in these reports. Frequently, staff from transplant programs make public comments regarding these reports, made available in the comments page. We encourage all readers of these reports to consider these comments and to contact the program directly for further information.

Table Details:

The above overview provides most readers with a quick look at some of the statistics that help describe a transplant program. The following section, for the more interested reader, provides a more detailed accounting of each table and how figures are defined and calculated.

Tables 1 through 6 focus on characteristics of the waiting list process at this center. Table 1 provides an overview of the waiting list activity at this center: not just the size of the waiting list at a given point in time, but also how many people have moved on to and off of this waiting list, and for what reasons. Shown as a percentage of the total waiting list size on 01/01/2002, the percent of people removed for a transplant from a deceased donor was 68.2%, (vs. 27.0% nationwide) and the percentage of people removed because of death was 24.2% (vs. 9.9% nationwide). Table 2 shows the characteristics of patients on the waiting list at Nebraska Health System.

The waiting time at a given transplant center is affected by many factors, including the medical condition and characteristics of the patients listed with this center (Table 2), the availability of organs in the Donation Service Area served by the OPO, and decisions by medical professionals and other patients about organ acceptance. Some of the variability in waiting time may be accounted for by local availability of organs, in which case other centers in the Donation Service Area served by Nebraska Organ Retrieval System may have similar waiting times.

Tables 3 through 6 provide different measures of looking at waiting list outcomes. Table 3 shows a 'risk-adjusted' comparison of two outcomes from the waiting list: transplant rate and death rate. While the national average transplant rate (from deceased donors) is 0.29 transplants per patient year, the rate expected for this center is 0.59. The difference, or 'adjustment', between the national average and expected rate is caused by the fact that this center may treat patients who typically have longer (or shorter) waiting times, based on the characteristics of these patients. The patients on the waiting list at this center experienced a transplant rate of 0.71 per year spent on the waiting list for any person(s) on the waiting list. Compared to the expected rate of 0.59, the difference is not statistically significant (p>.05); there is a good possibility that it is due to random chance.

These waiting list rates are measured as the number of transplants (or deaths) per year that any patient spends on the waiting list. It is possible for these rates to be above 1, as would be the case if 2 patients each spent 3 months on the waiting list, and one received a transplant: 1 transplant divided by .5 year = transplant rate of 2.

While Table 3 provides a waiting list outcome rate that allows easy comparison of risk-adjusted outcomes, statistics from tables 4 through 6 may be more interpretable at a patient level. Table 4 answers the questions: 'What has been the outcome for patients at this center 6 months after being placed on the waiting list? What about at 12 or 18 months?' The table also examines post-transplant outcomes: at 12 months, for example, the table tells if the patient is still on the waiting list, was transplanted and is still alive, or died after transplant. Outcomes from this table are described above in the 'Overview' section.

Table 5 provides another way to look at how quickly patients receive transplants at this center, this time looking at many different kinds of patients. At this center, 12.5 percent of patients placed on the liver waiting list had received transplants as of 30 days after being placed on the waiting list. Those not transplanted, the other 87.5 percent, were either still waiting or removed from the waiting list for reasons including death. At one year after placement on the waiting list, 41.2 percent of patients at this center had been transplanted; this figure was 35.1 for all the centers in the nation. The table also shows similar figures for subgroups of patients, such as by age, disease, or medical urgency, allowing the reader to see if specific groups of patients have experienced longer waiting times.

Table 6 shows the time it takes for a given percentage of patients at this facility to receive a transplant. This is the 'time-to-transplant' among all wait-listed patients, including those who never receive a transplant. Half of the patients placed on the waiting list at this center had received a transplant as of 12.0 months after listing; in the nation it took 67.1 months to reach the same fraction. The other half of the patients were either still waiting or removed from the waiting list, for reasons including death. (Another common statistic, 'median waiting time,' differs in that it is often calculated only among patients who actually received a transplant. The two are often correlated, but different in magnitude. While median waiting time reflects time waiting among successful candidates, time-to-transplant incorporates a measure of the probablility of success in receiving an organ.)

The remainder of the tables, 7 through 11, focus on transplants performed at Nebraska Health System and their outcomes. Tables 7-9 describe the characteristics of transplant recipients, donors, and operations at this center.

Tables 10 and 11 show post-transplant outcomes. Table 10 shows the survival experience of grafts (transplants) in patients transplanted by this center. Table 11 shows the survival experience of these patients themselves. These may be different because a patient may continue survival after a graft fails through means such as a new transplant, or, for kidney patients, dialysis. For each outcome, these tables show an actual (observed) survival for the center, an actual (observed) survival for the nation, and an expected survival for the center. Each survival number measures the percentage of patients who have a functioning graft (Table 10) or who are alive (Table 11) at 1 month, 1 year, and 3 years after transplant.

The expected survival rate for a given center is the percentage of grafts functioning (or patients alive) that would be expected for the patients served by this center, given their characteristics (age, disease, blood type, etc.) and the experience of similar patients in the entire country. At this center, the expected one-year patient survival rate of 87.40 may be different from the national average of 86.55 if patients transplanted at this center have characteristics that would make us expect a different survival rate than the average.