Screening for abdominal aortic aneurysm

An aneurysm is a localised widening (dilation) of an artery. The blood vessel can burst (rupture) because the vessel wall is weakened. Some 5% to 10% of men aged between 65 and 79 years have an abdominal aneurysm in the area of the aorta, the main artery from the heart as it passes through the abdomen. Abdominal aortic aneurysms are often asymptomatic but a rupture is a surgical emergency and often leads to death. An aneurysm larger than 5 cm carries a high risk of rupture. Smaller aneurysms are monitored regularly using ultrasound to see if they are becoming larger. Elective surgical repair of aortic aneurysms aims to prevent death from rupture. The incidence of aortic aneurysm in women as they age is lower than for men.

This review identified four controlled trials involving 127,891 men and 9342 women who were randomly assigned to aortic aneurysm screening using ultrasound or no screening. Only one trial included women. Two of the trials were conducted in the UK, one in Denmark and one in Australia. The results provide evidence of a benefit from screening in men with a strongly significant reduction in deaths from abdominal aortic aneurysm. The odds ratio (OR) for death was 0.60 (range 0.47 to 0.78, three trials) in men aged 65 to 83 years but was not reduced for women. From one trial there was also a decreased incidence of ruptured aneurysm in men but not women.

All-cause mortality was not significantly different between screened and unscreened groups some three to five years after screening, which is to be expected given the relative infrequency of abdominal aortic aneurysm as a cause of death.

Men who had been screened underwent more surgery for abdominal aortic aneurysm (OR 2.03; range 1.59 to 2.59, four trials) but resource analysis appears to demonstrate overall cost effectiveness of screening. There were no data on life expectancy, complications of surgery or quality of life.

Authors' conclusions: 

There is evidence of a significant reduction in mortality from AAA in men aged 65 to 79 years who undergo ultrasound screening. There is insufficient evidence to demonstrate benefit in women. The cost effectiveness may be acceptable, but needs further expert analysis. These findings need careful consideration in judging whether a co-ordinated population-based screening programme should be introduced.

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Background: 

Abdominal aortic aneurysm (AAA) is found in 5% to 10% of men aged 65 to 79 years. The major complication is rupture which presents as a surgical emergency. The mortality after rupture is high, 80% for patients reaching hospital and 50% for those undergoing surgery for emergency repair. Currently elective surgical repair is recommended for aneurysms discovered to be larger than 5.5 cm to prevent rupture. There is interest in population screening to detect, monitor and repair abdominal aortic aneurysms before rupture.

Objectives: 

To determine the effects of screening asymptomatic individuals for AAA on mortality, subsequent treatment, quality of life and cost effectiveness of screening.

Search strategy: 

The Cochrane Peripheral Vascular Diseases Group searched their Trials Register (last searched 27 July 2007) and CENTRAL (last searched 2007, Issue 3).

Selection criteria: 

Randomised controlled trials of population screening for AAA.

Data collection and analysis: 

Two authors independently assessed trials and extracted data.

Main results: 

Four studies involving 127,891 men and 9342 women were included in this review. Only one study included women.

Results for men and women were analysed separately. Three to five years after screening there was no significant difference in all-cause mortality between screened and unscreened groups for men or women (men, odds ratio (OR) 0.95; 95% Confidence interval (CI) 0.85 to 1.07; for women OR 1.06; 95% CI 0.93 to 1.21).

There was a significant decrease in mortality from AAA in men (OR 0.60; 95% CI 0.47 to 0.78), but not for women (OR 1.99; 95% CI 0.36 to 10.88). In this analysis mortality includes death from rupture and from emergency or elective surgery for aneurysm repair. There was also a decreased incidence of ruptured aneurysm in men (OR 0.45; 95% CI 0.21 to 0.99) but not in women (OR 1.49; 95% CI 0.25 to 8.94).

There was a significant increase in surgery for AAA in men (OR 2.03; 95% CI 1.59 to 2.59). This was not reported in women. There were no data on life expectancy, complications of surgery or subjective quality of life.

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