Survival After Pancreas TransplantationSurvival After Pancreas Transplantation

To the Editor: We would like to raise concerns about 3 possible flaws in the design and analysis of the study by Dr Venstrom and colleagues.¹ First, patients listed for a pancreas transplant at multiple centers, as well as those who changed centers, were counted more than once. When we reviewed the United Network for Organ Sharing (UNOS) database and identified patients who had more than 1 listing for the same organ(s) at different centers, had changed centers, had refused a transplant offer but were subsequently relisted, were listed on both the pancreas transplant–alone and the simultaneous pancreas-kidney transplant lists and had not received a kidney transplant alone, had been removed from the waiting list for medical or other reasons but were subsequently relisted or were still listed but had undergone a successful transplant at a different center, we concluded that 12% of all patients listed had been counted more than once.

Second, the article did not mention that 6% of recipients listed for a pancreas transplant alone and 10% of those listed for a simultaneous pancreas-kidney transplant actually underwent a kidney transplant alone; those patients should have been recategorized. Third, the study excluded patients on the pancreas transplant–alone waiting list initially reported to have a serum creatinine level greater than 2 mg/dL (176.8 μmol/L). However, before October 1999, reporting of creatinine levels for such transplants was not required by the UNOS, and our review of the UNOS database indicates that 62% of creatinine levels at the time of listing were missing and could only be assumed to be less than 2 mg/dL. The exact time of serum creatinine measurements reported to the UNOS is unknown, so samples may have been obtained months before listing, and changes in kidney function for waiting patients are not reported to the UNOS. Our review of the UNOS database found that in 42% of pancreas-after-kidney listings with creatinine levels greater than 2 mg/dL, the level was from before or at the time of the kidney transplant, leading to inappropriate exclusion from the analysis.

We believe that this study design leads to falsely low estimations of waiting-list mortality. We reanalyzed the data,² correcting for multiple listings, recipient category misclassifications, and creatinine exclusions. We examined the same time period (January 1, 1995, through December 31, 2000) and the same follow-up period (1460 days for transplant recipients and 1460 days plus the median waiting time for those not receiving a transplant). Our results indicate that the study by Venstrom et al underestimated 4-year mortality by 4%, 6%, and 6% in the pancreas transplant–alone, pancreas-after-kidney, and simultaneous pancreas-kidney categories, respectively. We found that the overall mortality in all 3 categories was not increased after transplantation and that after the first year the hazard ratios were significantly decreased for transplanted vs wait-listed patients in all 3 categories (P<.001). Our conclusion is that the mortality for solitary pancreas transplant recipients is not higher than for wait-listed patients.