Population based randomised controlled trial on impact of screening on mortality from abdominal aortic aneurysm

Abstract

Objective: To assess whether screening for abdominal aortic aneurysms in men reduces mortality.

Design: Population based randomised controlled trial of ultrasound screening, with intention to treat analysis of age standardised mortality.

Setting: Community based screening programme in Western Australia.

Participants: 41,000 men aged 65-83 years randomised to intervention and control groups.

Intervention: Invitation to ultrasound screening.

Main outcome measure: Deaths from abdominal aortic aneurysm in the five years after the start of screening.

Results: The corrected response to invitation to screening was 70%. The crude prevalence was 7.2% for aortic diameter > or = 30 mm and 0.5% for diameter > or = 55 mm. Twice as many men in the intervention group than in the control group underwent elective surgery for abdominal aortic aneurysm (107 v 54, P = 0.002, chi2 test). Between scheduled screening and the end of follow up 18 men in the intervention group and 25 in the control group died from abdominal aortic aneurysm, yielding a mortality ratio of 0.61 (95% confidence interval 0.33 to 1.11). Any benefit was almost entirely in men aged between 65 and 75 years, where the ratio was reduced to 0.19 (0.04 to 0.89).

Conclusions: At a whole population level screening for abdominal aortic aneurysms was not effective in men aged 65-83 years and did not reduce overall death rates. The success of screening depends on choice of target age group and the exclusion of ineligible men. It is also important to assess the current rate of elective surgery for abdominal aortic aneurysm as in some communities this may already approach a level that reduces the potential benefit of population based screening.

Fig 1

Summary of trial of screening for abdominal aortic aneurysm

Fig 2

Cumulative mortality due to abdominal aortic aneurysm after date of screening

Fig 3

Cumulative mortality due to abdominal aortic aneurysm after date of randomisation

Fig 4

Cumulative all cause mortality after date of screening

Fig 5

Cumulative all cause mortality from date of randomisation