European best practice guidelines for renal transplantation. Section IV: Long-term management of the transplant recipient. IV.13 Analysis of patient and graft survival.
GUIDELINES: A. It is important for a transplant unit to follow-up on the results of their transplant activities. In order to achieve correct reports on graft and patient outcome in all patients, it is necessary to have sufficient resources, such as a computerized database, and continuous updates of patient information. All data collected should be subjected to validation procedures to ensure completeness and accuracy. B. Improved outcomes following implementation of new protocols, based on evaluation of clinical multi-centre trials, should be verified at local transplant centres since centres often include a range of patients different from those selected for the trial. C. The most widely accepted descriptor of outcome is the Kaplan-Meier probability estimate of patient and graft survival. Survival estimates should be calculated at intervals of time after transplantation and should always be expressed with their 95% confidence intervals. D. Kaplan-Meier survival estimates may be calculated in three ways. (i) 'Patient survival' should be calculated from the date of transplantation to the date of death or the date of the last follow-up. (ii) 'Graft survival' (non-censored for death) should be calculated from the date of transplantation to the date of irreversible graft failure signified by return to long-term dialysis (or retransplantation) or the date of the last follow-up during the period when the transplant was still functioning or to the date of death. Here, death with graft function is treated as graft failure. (iii) 'Graft survival censored for death with a functioning graft' (death-censored graft survival) should be calculated from the date of transplantation to the date of irreversible graft failure signified by return to long-term dialysis (or retransplantation) or the date of last follow-up during the period when the transplant was still functioning. In the event of death with a functioning graft, the follow-up period is censored at the date of death. E. The outcome of transplants carried out at a centre should be compared with those achieved across a range of data from centres collated by national and international multi-centre registries. Interpretation of a centre's performance should take into account the number of transplants performed and the prevalence of major risk factors. F. Major risk factors that influence transplant outcome are identifiable by applying multivariate analytical methods to large multi-centre follow-up databases. Although these major risk factors may not be identifiable in individual centre data, they should nonetheless be taken into account in patient management. G. When designing a clinical trial or evaluating data from a recent trial, the expected improvement in graft survival resulting from a reduction in acute rejection may be estimated from a knowledge of the rejection and graft survival rates that existed prior to the introduction of the new therapeutic regimen. H. When designing or evaluating a clinical trial, it is important to analyse the power of the study to verify statistically the difference (in graft survival) that might be expected and its statistical significance. A study resulting in absence of statistically significant differences between two treatment groups with insufficient statistical power to verify a difference at the expected level should not be taken as evidence of absence of a true difference.