Clinical effectiveness and cost-effectiveness of collaborative care for depression in UK primary care (CADET): a cluster randomised controlled trial

Background: Collaborative care is effective for depression management in the USA. There is little UK evidence on its clinical effectiveness and cost-effectiveness. Objective: To determine the clinical effectiveness and cost-effectiveness of collaborative care compared with usual care in the management of patients with moderate to severe depression. Design: Cluster randomised controlled trial. Setting: UK primary care practices (n = 51) in three UK primary care districts. Participants: A total of 581 adults aged = 18 years in general practice with a current International Classification of Diseases, Tenth Edition depressive episode, excluding acutely suicidal people, those with psychosis, bipolar disorder or low mood associated with bereavement, those whose primary presentation was substance abuse and those receiving psychological treatment. Interventions: Collaborative care: 14 weeks of 6-12 telephone contacts by care managers; mental health specialist supervision, including depression education, medication management, behavioural activation, relapse prevention and primary care liaison. Usual care was general practitioner standard practice. Main outcome measures: Blinded researchers collected depression [Patient Health Questionnaire-9 (PHQ-9)], anxiety (General Anxiety Disorder-7) and quality of life (European Quality of Life-5 Dimensions three-level version), Short Form questionnaire-36 items) outcomes at 4, 12 and 36 months, satisfaction (Client Satisfaction Questionnaire-8) outcomes at 4 months and treatment and service use costs at 12 months. Results: In total, 276 and 305 participants were randomised to collaborative care and usual care respectively. Collaborative care participants had a mean depression score that was 1.33 PHQ-9 points lower [n = 230; 95% confidence interval (CI) 0.35 to 2.31; p = 0.009] than that of participants in usual care at 4 months and 1.36 PHQ-9 points lower (n = 275; 95% CI 0.07 to 2.64; p = 0.04) at 12 months after adjustment for baseline depression (effect size 0.28, 95% CI 0.01 to 0.52; odds ratio for recovery 1.88, 95% CI 1.28 to 2.75; number needed to treat 6.5). Quality of mental health but not physical health was significantly better for collaborative care at 4 months but not at 12 months. There was no difference for anxiety. Participants receiving collaborative care were significantly more satisfied with treatment. Differences between groups had disappeared at 36 months. Collaborative care had a mean cost of 272.50 pound per participant with similar health and social care service use between collaborative care and usual care. Collaborative care offered a mean incremental gain of 0.02 (95% CI -0.02 to 0.06) quality-adjusted life-years (QALYs) over 12 months at a mean incremental cost of 270.72 pound (95% CI -202.98 pound to 886.04) pound and had an estimated mean cost per QALY of 14,248 pound, which is below current UK willingness-to-pay thresholds. Sensitivity analyses including informal care costs indicated that collaborative care is expected to be less costly and more effective. The amount of participant behavioural activation was the only effect mediator. Conclusions: Collaborative care improves depression up to 12 months after initiation of the intervention, is preferred by patients over usual care, offers health gains at a relatively low cost, is cost-effective compared with usual care and is mediated by patient activation. Supervision was by expert clinicians and of short duration and more intensive therapy may have improved outcomes. In addition, one participant requiring inpatient treatment incurred very significant costs and substantially inflated our cost per QALY estimate. Future work should test enhanced intervention content not collaborative care per se.