Background The UK's Quality and Outcomes Framework (QOF) was introduced in 2004/5, linking remuneration for general practices to recorded quality of care for chronic conditions, including diabetes mellitus. We assessed the effect of the incentives on recorded quality of care for diabetes patients and its variation by patient and practice characteristics.

Methods Using the General Practice Research Database we selected a stratified sample of 148 English general practices in England, contributing data from 2000/1 to 2006/7, and obtained a random sample of 653 500 patients in which 23 920 diabetes patients identified. We quantified annually recorded quality of care at the patient-level, as measured by the 17 QOF diabetes indicators, in a composite score and analysed it longitudinally using an Interrupted Time Series design.

Results Recorded quality of care improved for all subgroups in the pre-incentive period. In the first year of the incentives, composite quality improved over-and-above this pre-incentive trend by 14.2% (13.7–14.6%). By the third year the improvement above trend was smaller, but still statistically significant, at 7.3% (6.7–8.0%). After 3 years of the incentives, recorded levels of care varied significantly for patient gender, age, years of previous care, number of co-morbid conditions and practice diabetes prevalence.

Conclusions The introduction of financial incentives was associated with improvements in the recorded quality of diabetes care in the first year. These improvements included some measures of disease control, but most captured only documentation of recommended aspects of clinical assessment, not patient management or outcomes of care. Improvements in subsequent years were more modest. Variation in care between population groups diminished under the incentives, but remained substantial in some cases.