Journal Article

Estimation of renal allograft half-life: fact or fiction?

M. Antonieta Azancot, Carme Cantarell, Manel Perelló, Irina B. Torres and Daniel Serón

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 26, issue 9, pages 3013-3018
Published in print September 2011 | ISSN: 0931-0509
Published online February 2011 | e-ISSN: 1460-2385 | DOI:
Estimation of renal allograft half-life: fact or fiction?

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Introduction. Renal allograft half-life time (t½) is the most straightforward representation of long-term graft survival. Since some statistical models overestimate this parameter, we compare different approaches to evaluate t½.

Patients and methods. Patients with a 1-year functioning graft transplanted in Spain during 1990, 1994, 1998 and 2002 were included. Exponential, Weibull, gamma, lognormal and log-logistic models censoring the last year of follow-up were evaluated. The goodness of fit of these models was evaluated according to the Cox–Snell residuals and the Akaike’s information criterion (AIC) was employed to compare these models.

Results. We included 4842 patients. Real t½ in 1990 was 14.2 years. Median t½ (95% confidence interval) in 1990 and 2002 was 15.8 (14.2–17.5) versus 52.6 (35.6–69.5) according to the exponential model (P < 0.001). No differences between 1990 and 2002 were observed when t½ was estimated with the other models. In 1990 and 2002, t½ was 14.0 (13.1–15.0) versus 18.0 (13.7–22.4) according to Weibull, 15.5 (13.9–17.1) versus 19.1 (15.6–22.6) according to gamma, 14.4 (13.3–15.6) versus 18.3 (14.2–22.3) according to the log-logistic and 15.2 (13.8–16.6) versus 18.8 (15.3–22.3) according to the lognormal models. The AIC confirmed that the exponential model had the lowest goodness of fit, while the other models yielded a similar result.

Conclusions: The exponential model overestimates t½, especially in cohorts of patients with a short follow-up, while any of the other studied models allow a better estimation even in cohorts with short follow-up.

Keywords: death-censored allograft survival; kidney transplantation; median half-life

Journal Article.  3095 words.  Illustrated.

Subjects: Nephrology

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