Survival and dialysis initiation: comparing British Columbia and Scotland registries

Outcomes are a major metric for evaluating effectiveness of dialysis. Comparisons between different populations reveal significant variation. In addition, the question of optimal timing of dialysis start lacks robust data from which to generate conclusions.

This study compares dialysis survival in two geographically similar areas, Scotland and British Columbia, Canada (BC). The effect of eGFR at dialysis start on survival was also measured. Incident adult dialysis populations of Scotland (n = 3372) and BC (n = 3927), 2000-05 were compared. Mortality Hazard ratios (HR) were calculated using a Cox proportional hazards model. Multivariate analysis included pre-dialysis eGFR, registry, age, sex, dialysis modality, year of start, pre-dialysis haemoglobin and primary renal diagnosis.

Median survival times from start of dialysis were 38 (35-40) and 44 (42-47) months in Scotland and BC, respectively, giving an unadjusted mortality HR, Scotland versus BC, of 1.20 (95% C.I. 1.12-1.29). BC patients started dialysis at a higher eGFR (8.9 ml/min/1.73 m(2)) than Scotland (7.5 ml/min/1.73 m(2)), and prior to modelling higher starting eGFR was associated with higher mortality (1 ml/min/1.73 m(2) increase, HR = 1.028; 95% C.I. 1.021-1.035). BC patients were also older and had more diabetic renal disease. In multivariate analysis, lower starting eGFR was associated with better survival, and Scotland had greater mortality than BC. General population mortality and transplantation rate had only minor influence.

Concepts of 'late' versus 'early' start dialysis based on eGFR alone may need modification given the complexity and confounding reasons for dialysis initiation.