Young 2007.

Study characteristics
Methods	Interrupted time series study
Participants	334 primary health physicians members of the Rochester Individual Practice Association (RIPA)
Interventions	Rochester, New York (USA) Interventions: pay for performance. In 2001, RIPA began the process of establishing a pay‐for‐performance programme as part of its contract with Excellus Health Plan to provide professional services for the approximately 450,000 individuals enrolled in Excellus’ Blue Choice Health Maintenance Organization (HMO) insurance product. Each RIPA primary care physician was eligible for reward payments of up to approximately USD 15,000 depending on his or her relative ranking on a composite performance measure for the diabetes‐related tests and screens. Control: no explicit information, but may be salary. RIPA served as an umbrella organisation for its member physicians with responsibilities for contracting with health plans on behalf of its member physicians and developing arrangements by which member physicians were reimbursed for their services. Years 1999 to 2004, intervention happed in 2002, 3 time points for pre‐/postintervention
Outcomes	Quality of health care provision 4 diabetes performance measures: glycated haemoglobin check, urinalysis, lipoprotein density level check, eye exam. Glycated haemoglobin check: increase in level without significance, but post‐trend did not differ from the pre‐trend Urinalysis: increase in level without significance, but post‐trend did not differ from the pre‐trend LDL check: increase in level without significance, but post‐trend did not differ from the pre‐trend Eye exams: increase in levels (7 percentage point increase after 1 year of intervention, but the increase did not persist), post‐trend did not differ from the pre‐trend
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Intervention independent of other changes (ITS)	Low risk	The increase in the eye examination score of intervention programme (Rochester (New York) Individual Practice Association) was contrary to the trends observed in the eye examination scores in Health Employer Data Information System nationally and statewide during this period, which were largely flat from 2000 to 2002. The observed increase thus did not appear to be attributable to a secular trend.
Shape of the intervention effect pre‐specified (ITS)	Low risk	The point of analysis is clear, the intervention start time: 2002.
Intervention unlikely to affect data collection (ITS)	Unclear risk	The data used for analysis in this paper were from patient electronic records, which were not influenced by payment reform. However, it is unclear if GPs' recording was changed with the start of the new payment policy.
Knowledge of the allocated interventions adequately prevented (ITS)	Low risk	Outcomes were objective.
Incomplete outcome data adequately addressed (ITS)	Low risk	No missing outcome data
Study free from selective outcome reporting (ITS)	Low risk	All outcomes mentioned in the methods section were reported in the results section.
Other risk of bias (ITS)	Low risk	The study included physicians who were members of the health plan for all 6 years, and so does not account for the potential selection bias if poorly performing physicians chose not to participate or withdraw.