Katon 2004.

Study characteristics
Methods	The Pathways Study: a randomized trial of collaborative care in patients with diabetes and depression RCT (NA clusters and NA providers), conducted in 1) 9 GHC (Group Health Cooperative) primary care clinics from a large health maintenance organisation in western Washington were selected for the study. 2) The intervention was provided by a depression clinical specialist nurses in collaboration with psychiatrist and psychologist supervisors and primary care physicians. In United States of America. 2 arms: 1. Control (usual care) (control arm) and 2. Intervention (pathways case management) (intervention arm)
Participants	Control arm N: 165 Intervention arm N: 164, NA, NA Diabetes type: 3 Mean age: 58.35 ± NR % Male: 35.00 Longest follow‐up: 12 months
Interventions	Control arm: (usual care) 1) Patient education Intervention arm: (pathways case management) 1) Case management 2) Team change 3) Continuous quality improvement
Outcomes	Glycated haemoglobin
Funding source	This study was supported by grants MH4‐1739 and MH01643 from the National Institute of Mental Health Services Division, Bethesda, Md (Dr Katon)
Notes	—
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Using a computerised algorithm, patients were randomised to the intervention or usual care group.
Allocation concealment (selection bias)	Unclear risk	Not reported.
Patient's baseline characteristics (selection bias)	Low risk	There were no significant differences between groups in any variable (Table 1).
Patient's baseline outcomes (selection bias)	Low risk	There were no significant differences between groups in any variable (Table 1).
Incomplete outcome data (attrition bias)	High risk	The following percentages completed 3‐, 6‐ and 12‐month assessments: 3‐month assessment, 151 (91.5%) intervention patients and 154 (93.3%) usual care patients; 6‐month assessment, 143 (87.8%) intervention patients and 149 (90.9%) usual care patients; and 12‐month assessment, 146 (88.5%) intervention patients and 142 (86.1%) usual care patients. Number balanced but quite high. Reasons not reported.
Blinding of participants and personnel (performance bias) and of outcome assessors (detection bias)	Low risk	Objective outcome (HbA1c).
Selective reporting (reporting bias)	Unclear risk	No registered protocol. Results match methods.
Risk of contamination (other bias)	Unclear risk	Participants had enhanced usual care, since routine care patients were encouraged to discuss depression with their primary care physician. Primary care physicians treated both intervention and control patients, leaving room for a spillover effect due to potential physician improvements in knowledge and skills in treating depression. Primary care physicians at the GHC frequently prescribe antidepressant medication and can refer patients to the GHC Mental Health Services. Both intervention and usual care patients could also self‐refer to a GHC mental health care provider. Half of the usual care controls in this study received antidepressant.
Other bias	Low risk	None identified.