The 'centre effect' in nephrology: what do differences between nephrology centres tell us about clinical performance in patient management?

Improving the quality of care provided by nephrology centres to patients with kidney disease requires a clear understanding of how to compare performance after adjustment for case mix, combined with a detailed understanding of the structure and processes that are associated with the achievement of good clinical results. In this review, we discuss how to measure quality of care (using process or outcome measures), how to take case mix into account, how best to display comparisons between nephrology centres, and how to study the causes of real variations in quality between centres. This is a narrative review; we include examples from other fields in which the centre effect has been studied, including education.