Cost-utility of a specific collaborative group intervention for patients with functional somatic syndromes

Abstract Background Collaborative group intervention (CGI) in patients with functional somatic syndromes (FSS) has been shown to improve mental quality of life. Objective To analyse incremental cost-utility of CGI compared to enhanced medical care in patients with FSS. Methods An economic evaluation alongside a cluster-randomised controlled trial was performed. 35 general practitioners (GPs) recruited 300 FSS patients. Patients in the CGI arm were offered 10 group sessions within 3 months and 2 booster sessions 6 and 12 months after baseline. Costs were assessed via questionnaire. Quality adjusted life years (QALYs) were calculated using the SF-6D index, derived from the 36-item short-form health survey (SF-36). We calculated patients' net-monetary-benefit (NMB), estimated the treatment effect via regression, and generated cost-effectiveness acceptability curves. Results Using intention-to-treat analysis, total costs during the 12-month study period were 5777EUR in the intervention, and 6858EUR in the control group. Controlling for possible confounders, we found a small, but significant positive intervention effect on QALYs (+ 0.017; p  = 0.019) and an insignificant cost saving resulting from a cost-increase in the control group (− 10.5%; p  = 0.278). NMB regression showed that the probability of CGI to be cost-effective was 69% for a willingness to pay (WTP) of 0EUR/QALY, increased to 92% for a WTP of 50,000EUR/QALY and reached the level of 95% at a WTP of 70,375EUR/QALY. Subgroup analyses yielded that CGI was only cost-effective in severe somatic symptom severity (PHQ-15 ≥ 15). Conclusion CGI has a high probability to be a cost-effective treatment for FSS, in particular for patients with severe somatic symptom severity.