Halbert 1999.

Methods	RCT (design not clear randomised by patient) Randomisation concealment: NOT CLEAR Follow up: ‐ providers: N/A ‐ patients: NOT CLEAR Blinded assessment: DONE Baseline: NOT CLEAR Reliable outcomes: DONE Protection against contamination: DONE
Participants	Diabetic patients who were enrolled in a large network‐based Health Maintenance Organisation (HMO) in California (US) and the medical groups that treated the identified diabetic patients (Type 1 and Type 2 diabetes) providers ‐ ? patients ‐ 19,523 practices ‐ 1 Health Maintenance Organisation, the number of medical group is not clear
Interventions	Intervention group: Organisational intervention (arrangements for follow‐up) Control group: as in the intervention group, they received guidelines, a list of their diabetes patients with their diabetic retinopathy screening exam status and patients without a record of diabetic retinopathy exam received educational materials. In contrast with the patients in the intervention group who received multiple reminders, the patients received a single reminder
Outcomes	PROCESS: Rates of retinal examination PATIENT: NONE
Notes	National guidelines (ADA guidelines) ‐directed at monitoring ‐target: retinopathy screening
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment?	Unclear risk	B ‐ Unclear