Should interventions to reduce variation in care quality target doctors or hospitals?

Interventions to reduce variation in care quality are increasingly targeted at both individual doctors and the organisations in which they work. Concerns remain about the scope and consequences for such performance management, the relative contribution of individuals and organisations to observed variation, and whether performance can be measured reliably. This study explores these issues in the context of the English National Health Service by analysing comprehensive administrative data for all patients treated for four clinical conditions (acute myocardial infarction, hip fracture, pneumonia, ischemic stroke) and two surgical procedures (coronary artery bypass, hip replacement) during April 2010-February 2013. Performance indicators are defined as 30-day mortality, 28-day emergency readmission and inpatient length of stay. Three-level hierarchical generalised linear mixed models are estimated to attribute variation in case-mix adjusted indicators to individual doctors and hospital organisations. Except for length of stay after hip replacement, no more than 11% of variation in case-mix adjusted performance indicators can be attributed to doctors and organisations with the rest reflecting random chance and unobserved patient factors. Doctor variation exceeds hospital variation by a factor of 1.2 or more. However, identifying poor performance amongst doctors is hampered by insufficient numbers of cases per doctor to reliably estimate their individual performances. Policy makers and regulators should therefore be cautious when targeting individual doctors in performance improvement initiatives.