Doubling of serum creatinine in clinical trials, cost-effectiveness studies, and individual patients: adequate use in renal transplantation.

ABSTRACT

BACKGROUND: The predictive value of doubling of serum creatinine (DSC) has never been assessed in renal transplantation. We evaluated it in terms of its use for clinical trials, cost-effectiveness studies, and individual patients. METHODS: Retrospective longitudinal study in 896 renal transplant recipients. RESULTS: Death-censored graft loss occurred in 133 patients, during follow-up (up to 21 years). DSC was a risk factor for graft loss; however, the relative risk was different in patients with glomerular filtration rate less than 40 vs. more than or equal to 40 mL/min (hazard ratio 14.5 [95% confidence interval 7.4-28.4] vs. 47.8 [28.4-80.6], P=0.0051). Parameters influencing creatinine value (weight, age, sex) did not modify DSC's predictive value. The use of the composite endpoint DSC or death-censored graft loss instead of death-censored graft loss alone in clinical trials would reduce sample size by 7.1% to 9.0%. The annual probability of DSC to graft loss transition decreased from 76% (follow-up <1 year) to 5% (follow-up ≥10 years). Median graft half-life after DSC was 10 months [95% confidence interval 6-18] but varied with increasing time to DSC (<1 year 1 month [0.5-6]; 3-4.9 years 15 months 5/67) and reference creatinine (<130 µmol/L 3 months 2/6); ≥130 µmol/L 25 months 15/37). CONCLUSIONS: DSC may be adequately used to refine the risk of death-censored graft loss for individual patients. However, the use of DSC as an endpoint in clinical trials marginally affects sample size, and the probability of DSC to graft loss transition is not constant, which limits the use of DSC in cost-effectiveness analyses of renal transplantation.