Cluster randomised controlled trial comparing the effectiveness and cost-effectiveness of two primary care interventions aimed at improving attendance for breast screening.

Objectives - To examine the effectiveness and cost-effectiveness of two interventions based in primary care aimed at increasing uptake of breast screening. Setting - 24 General practices with low uptake in the second round of screening (below 60%) in north west London and the West Midlands, UK. Participants were all women registered with these practices and eligible for screening in the third round. Methods - Pragmatic factorial cluster randomised controlled trial, with practices randomised to a systematic intervention (general practitioner letter), an opportunistic intervention (flag in women's notes prompting discussion by health professionals), neither intervention, of both. Outcome measures were attendance for screening 6 months after the practices had been screened and cost-effectiveness of the interventions. Results - 6133 Women were included: 1721 control; 1818 letter; 1232 flag; 1362 both interventions. Attendance data were obtained for 5732 (93%) women. The two interventions independently increased breast screening uptake in a logistic regression model adjusted for clustering, with the flag (odds ratio (OR) 1.43, 95% confidence interval (95% CI) 1.14 to 1.79; p=0.0019) marginally more effective than the letter (OR 1.31, 95% CI 1.05 to 1.64; p=0.015). Health service costs per additional attendance were £26 (letter) and £41 (flag). Conclusions - Although both interventions increased attendance for breast screening, the letter was the more cost-effective. Any decision to implement both interventions rather than just the letter will depend on whether the additional (£41) costs ate judged worthwhile in terms of the gains in breast screening uptake.