Multicentre aneurysm screening study (MASS): cost effectiveness analysis of screening for abdominal aortic aneurysms based on four year results from randomised controlled trial

Abstract

Objective: To assess the cost effectiveness of ultrasound screening for abdominal aortic aneurysms.

Design: Primary analysis: four year cost effectiveness analysis based directly on results from a randomised controlled trial in which patients were individually allocated to invitation to ultrasound screening (intervention) or to a control group not offered screening. Secondary analysis: projection of the data, based on conservative assumptions, to indicate likely cost effectiveness at 10 years.

Setting: Four centres in the United Kingdom. Screening delivered in primary care settings with follow up and surgery offered in the main hospitals Participants: Population based sample of 67 800 men aged 65-74 years.

Main outcome measures: Mortality from and costs (screening, follow up, elective and emergency surgery) related to abdominal aortic aneurysm; cost per life year gained.

Results: Over four years there were 47 fewer deaths related to abdominal aortic aneurysms in the screening group than in the control group, but the additional costs incurred were pound 2.2m. After adjustment for censoring and discounted at 6% the mean additional cost of the screening programme was pound 63.39 ($97.77, euro;100.48) (95% confidence interval pound 53.31 to pound 73.48) per patient. The hazard ratio for abdominal aortic aneurysm was 0.58 (0.42 to 0.78). Over four years the mean incremental cost effectiveness ratio for screening was pound 28 400 ( pound 15 000 to pound 146 000) per life year gained, equivalent to about pound 36 000 per quality adjusted life year. After 10 years this figure is estimated to fall to around pound 8000 per life year gained.

Conclusions: Even at four years the cost effectiveness of screening for abdominal aortic aneurysms is at the margin of acceptability according to current NHS thresholds. Over a longer period the cost effectiveness will improve substantially, the predicted ratio at 10 years falling to around a quarter of the four year figure.

Figure 1

Costs per six month period (C=control; I=intervention)

Figure 2

Mortality related to abdominal aortic aneurysms over four years of follow up by randomised group

Figure 3

Cost effectiveness acceptability curves (probability that screening is cost effective after four years plotted as function of sum willing to be paid per life year gained) for base case and key sensitivity analyses, based on four years of follow up