Comparing dialysis centre mortality outcomes across Australia and New Zealand: Identifying unusually performing centres 2008-2013

Background: Comparing the mortality profiles of dialysis centres is important to ensure that high standards of care are maintained. We compare the performance of dialysis centres in Australia and New Zealand in their treatment of haemodialysis patients, accounting for the competing risks of kidney transplantation and transfer to peritoneal dialysis. Methods: Observational cohort study. We included data from all adult patients (5574 patients) commencing haemodialysis at home or in a facility between 2008 and 2010 across 62 dialysis centres, from the Australia and New Zealand Dialysis and Transplant Registry. Standardised mortality ratios were calculated by estimating mortality probabilities from a pooled random effects logistic regression model, accounting for the competing risk of transplantation using an inverse probability weighting approach. Models were adjusted for patient comorbidities, sex, height, weight, late referral to a nephrologist, age, race, primary kidney disease, smoking status, and serum creatinine (μmol/l). Results: Two dialysis centres were found to have relatively higher levels of risk-adjusted mortality lying outside the prediction intervals for "usual" performance. Risk adjusted mortality rates were not associated with centres' compliance with guidelines for vascular access and biochemical and haematological targets. Conclusions: We demonstrate that standardised mortality ratios are useful to identify facilities that have statistically outlying mortality risk. Our criterion for determining whether a centre has better or worse performance than expected is statistical, and thus analyses such as ours can serve only as a screening tool, and are only one aspect of assessment of "quality" of performance.