Functional status and mortality in chronic kidney disease: results from a prospective observational study

Measures of functional status are used in the general population to aid prognostication but their use has not been explored in pre-dialysis chronic kidney disease (CKD). This analysis considers the association between the Karnofsky performance score (KPS) and all-cause mortality in a CKD stage 3-5 cohort.

Patients were selected from the Chronic Renal Insufficiency Standards Implementation Study (CRISIS), a prospective observational study of outcome in CKD. Risk for death was assessed using multivariate Cox regression, and differences in progression of biochemical parameters were considered in a mixed-effects model.

A total of 1,515 patients with a median follow-up time of 2.9 (1.5-4.8) years were considered. Baseline age was 60 ± 11 years and eGFR was 30 ± 12 ml/min/1.73 m(2). Patients with a reduced KPS had an increased risk for death. The hazard ratio (HR) for death was: KPS 90 group, HR 1.2 (95% CI 0.9-1.5), p = 0.1; KPS ≤ 80 group, HR 1.8 (95% CI 1.4-2.4), p < 0.001. In the mixed-effects model, the average annual loss of eGFR was greater in patients with a KPS ≤ 80 versus patients with a KPS >80 (5 vs. 3%, p = 0.008).

A reduced KPS is independently associated with risk for mortality in patients with CKD stages 3-5. This may relate to a more rapid loss of eGFR.