Quality measurement of care for people with type 2 diabetes in Tayside, Scotland:implications for the new UK general practice contract

Background: The new United Kingdom general practice contract proposes that up to a third qf general practitioners' income will come from achieving quality targets. Aim: To examine selected quality markers in terms of their robustness to case-mix variation and chance effects, and in the attribution of quality to practices. Study design and methods: Data were extracted from a population-based diabetes clinical information system in Tayside, Scotland, for patients with type 2 diabetes registered in 67 practices with complete ascertainment. Results: Most practices would have received relatively high levels of payment for the process measures examined. Outcome measures appeared more challenging. Case-mix adjustment for age, sex, and postcode-assigned deprivation altered measured performance by up to 7%, but payment by up to 14%. Despite no strong evidence of any real difference in quality, chance effects meant that there was greater apparent variability for smaller practices from year to year. Hospital attendance was common, but highly variable between practices. Conclusion: Case-mix adjustment to allow fairer comparison is routine in national performance indicators, and ignoring it risks making the new contract quality framework inequitable. Because of chance effects, smaller practices may have greater year-to-year variability in income. Reflecting National Health Service structure, the new contract provides no incentives for integrated care and offers a perverse incentive to refer more patients to hospital. There are trade-offs between the validity qf measures, and the cost and bureaucracy of collecting data. The planned evaluation of the new contract should examine the effectiveness and equity of the quality framework, and rapidly act on deficiencies found.