Cost-effectiveness of Identification and Referral to Improve Safety (IRIS), a domestic violence training and support programme for primary care: a modelling study based on a randomised controlled trial

OBJECTIVE The Identification and Referral to Improve Safety (IRIS) cluster randomised controlled trial tested the effectiveness of a training and support intervention to improve the response of primary care to women experiencing domestic violence (DV). The aim of this study is to estimate the cost-effectiveness of this intervention. DESIGN Markov model-based cost-effectiveness analysis. SETTING General practices in two urban areas in the UK. PARTICIPANTS Simulated female individuals from the general UK population who were registered at general practices, aged 16 years and older. INTERVENTION General practices received staff training, prompts to ask women about DV embedded in the electronic medical record, a care pathway including referral to a specialist DV agency and continuing contact from that agency. The trial compared the rate of referrals of women with specialist DV agencies from 24 general practices that received the IRIS programme with 24 general practices not receiving the programme. The trial did not measure outcomes for women beyond the intermediate outcome of referral to specialist agencies. The Markov model extrapolated the trial results to estimate the long-term healthcare and societal costs and benefits using data from other trials and epidemiological studies. RESULTS The intervention would produce societal cost savings per woman registered in the general practice of UK£37 (95% CI £178 saved to a cost of £136) over 1 year. The incremental quality-adjusted life-year was estimated to be 0.0010 (95% CI -0.0157 to 0.0101) per woman. Probabilistic sensitivity analysis found 78% of model replications under a willingness to pay threshold of £20 000 per quality-adjusted life-year. CONCLUSIONS The IRIS programme is likely to be cost-effective and possibly cost saving from a societal perspective. Better data on the trajectory of abuse and the effect of advocacy are needed for a more robust model. TRIAL REGISTRATION Current Controlled Trials, ISRCTN74012786.