Using renal transplantation to evaluate a simple approach for predicting the impact of end-stage renal disease therapies on patient survival: observed/expected life span.

The effectiveness of therapy for a chronic disease can be assessed by evaluating the length of time that a patient survives after receiving treatment. We used a novel means for measuring the effectiveness of renal replacement therapy for patients with end-stage renal disease (ESRD): the ratio of observed life span divided by expected life span. This ratio incorporated observed life span for patients from the time of ESRD and expected life span based on state-specific life-table analyses. A total of 3,782 individuals with ESRD were analyzed (average follow-up, 14.2 +/- 4.9 years); 3, 192 patients in that group received a kidney transplant at some point during their course of ESRD. For each patient, we determined a curve of observed/expected life span. Separate patient groups were analyzed to determine the median population observed/expected life span or the percentage of patients who reached 0.5 observed/expected life span. Younger transplant recipients (<21 years) had a median observed/expected life span of 67%, significantly greater than the median observed/expected life span for those aged 21 to 40 years (49%; P = 0.01) and 41 to 60 years (47%; P = 0.01). Surprisingly, 57% of the patients aged older than 60 years reached their median observed/expected life span (P = 0.02 versus <21 years; P = not significant against all others). A Cox proportional hazards model identified era of immunosuppression (hazards ratio, 0.32) and atherosclerotic vascular disease-related ESRD (hazards ratio, 2.07) as significant variables influencing patient survival and observed/expected life span. This simple ratio is easy to use and may be a helpful tool for assessing the survival benefits of risk-factor modifications and therapeutic advances in transplantation and ESRD care.