Correspondence

Mortality among Patients on Dialysis, Patients on Dialysis Awaiting Transplantation, and Transplant Recipients

N Engl J Med 2000; 342:893-894March 23, 2000

Article

To the Editor:

The analysis by Wolfe et al. (Dec. 2 issue)1 purports to demonstrate a survival benefit of cadaveric renal transplantation as compared with hemodialysis for patients with end-stage renal disease. We agree that these data lend strong support to those who advocate renal transplantation and organ donation as a means to prolong life (in addition to improving the quality of life) in such patients. However, several points need clarification.

First, why were Hispanic patients excluded from the study? The percentage of Hispanic patients entering programs for end-stage renal disease is increasing, and it is important to determine how much they benefit from cadaveric renal transplantation.

Second, it appears that comparisons were made between the total group of 46,164 patients who were on the waiting list for transplantation and the 23,275 of these patients who received a cadaveric renal transplant. This comparison is similar to that made in an earlier study by the authors.2 Would it be more valid to compare the patients on the waiting list who did not receive a transplant with those who did receive a transplant? In another study,3 this group compared 554 patients on the waiting list (who had not received a transplant) with 236 patients who had received a transplant.

Third, the authors conducted an intention-to-treat analysis to eliminate bias in favor of patients on the waiting list who did not undergo transplantation. However, many patients become sicker while on the waiting list and are subsequently denied transplantation by their attending physicians. To what degree, then, does the intention-to-treat analysis bias the results in favor of transplant recipients?

Finally, were patients with combined kidney–pancreas transplants included? Data for these patients may be relevant, since the waiting time for combined transplantation is much shorter than that for kidney transplantation alone, and the receipt of a pancreas transplant may improve survival independently of the receipt of a renal transplant.

Raul A. Gatchalian, M.D.
David J. Leehey, M.D.
Loyola University Medical Center, Maywood, IL 60153

3 References

1. 1

   Wolfe RA, Ashby VB, Milford EL, et al. Comparison of mortality in all patients on dialysis, patients on dialysis awaiting transplantation, and recipients of a first cadaveric transplant. N Engl J Med 1999;341:1725-1730
   Full Text | Web of Science | Medline

2. 2

   Port FK, Wolfe RA, Mauger EA, Berling DP, Jiang K. Comparison of survival probabilities for dialysis patients vs cadaveric renal transplant recipients. JAMA 1993;270:1339-1343
   CrossRef | Web of Science | Medline

3. 3

   Ojo AO, Port FK, Wolfe RA, Mauger EA, Williams L, Berling DP. Comparative mortality risks of chronic dialysis and cadaveric transplantation in black end-stage renal disease patients. Am J Kidney Dis 1994;24:59-64
   Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: Drs. Gatchalian and Leehey request clarification that will help readers understand the results of our article. First, Hispanic ethnic background was not recorded in the data from the Health Care Financing Administration that we used in the analysis, so this characteristic was not accounted for in the analysis, although such patients were included. Analyses based on recent Health Care Financing Administration data, which include information on Hispanic ethnic background that is separate from the information on race, have not shown a substantial relation between Hispanic ethnic background and mortality among patients on dialysis.1

Second, the suggested comparison of mortality among patients on the waiting list who received a transplant with that among patients who did not receive a transplant would yield a seriously biased result. The bias that results from this type of analysis has been discussed extensively in the statistical literature with regard to heart-transplant recipients.2 The survival of patients on dialysis before transplantation should not be ignored or incorrectly ascribed to the transplantation group. We used a time-dependent analysis that switches patients from the dialysis group to the transplantation group at the time of transplantation and leads to the correct treatment assignment in the analysis.

Third, the intention-to-treat analysis was applied to both the transplantation and dialysis groups — that is, transplant recipients remained in the transplantation group, even if transplantation failed. Similarly, all deaths that occurred among patients on dialysis after placement on the waiting list were ascribed to the dialysis group. One can understand the error that results from removing patients from the analysis when they are removed from the waiting list by considering what would happen if close surveillance of health status led to the removal of patients from the waiting list whenever they got sick. In this case, patients would always be removed from the waiting list before they died, resulting in a mortality rate of 0 percent among the patients on dialysis who were on the waiting list.

Finally, our analysis did not distinguish recipients of combined kidney and pancreas transplants from those who received a kidney transplant alone. Only results for the group of diabetic patients with end-stage renal disease who were 20 to 39 years of age would be affected by the inclusion of this factor in the analysis, because in most patients with type 1 diabetes, end-stage renal disease begins before the age of 40 years.3

Robert A. Wolfe, Ph.D.
Valarie B. Ashby, M.A.
Friedrich K. Port, M.D.
University of Michigan, Ann Arbor, MI 48103

3 References

1. 1

   National Institute of Diabetes and Digestive and Kidney Diseases. United States Renal Data System: USRDS 1999 annual data report. Bethesda, Md.: National Institutes of Health, April 1999.
   

2. 2

   Aitkin M, Laird N, Francis B. A reanalysis of the Stanford heart transplant data. J Am Stat Assoc 1983;78:264-274
   CrossRef | Web of Science

3. 3

   Cowie CC, Port FK, Wolfe RA, Savage PJ, Moll PP, Hawthorne VM. Disparities in incidence of diabetic end-stage renal disease according to race and type of diabetes. N Engl J Med 1989;321:1074-1079
   Full Text | Web of Science | Medline

Citing Articles (5)

Citing Articles

1. 1

   E. Canet, J. Dantal, G. Blancho, M. Hourmant, S. Coupel. (2011) Tuberculosis following kidney transplantation: clinical features and outcome. A French multicentre experience in the last 20 years. Nephrology Dialysis Transplantation 26:11, 3773-3778
   CrossRef

2. 2

   Jennifer H. Kuo, Michael S. Wong, Richard V. Perez, Chin-Shang Li, Tzu-Chun Lin, Christoph Troppmann. (2011) Renal Transplant Wound Complications in the Modern Era of Obesity. Journal of Surgical Research
   CrossRef

3. 3

   A. Lopes, I.C. Frade, L. Teixeira, C. Oliveira, M. Almeida, L. Dias, A.C. Henriques. (2011) Depression and Anxiety in Living Kidney Donation: Evaluation of Donors and Recipients. Transplantation Proceedings 43:1, 131-136
   CrossRef

4. 4

   David Steinberg. (2004) An “Opting In” Paradigm for Kidney Transplantation. The American Journal of Bioethics 4:4, 4-14
   CrossRef

5. 5

   Salim Mujais, Lee Henderson. (2003) The uremic syndrome: Therapeutic-evaluative discordance. Kidney International 63:s84, 2-5
   CrossRef