Aneurysm screening saves lives, but cost-effective?

The results of a UK study suggest that screening older men for abdominal aortic aneurysm (AAA) provides a lasting survival benefit and becomes cost-effective over time. However, in a Danish study, screening for AAA in older men did not seem to be cost-effective.

An AAA occurs when the abdominal aortic artery becomes enlarged or balloons out, and there is a possibility of rupture or dissection before it is corrected surgically. Descending from the aorta in the heart, the abdominal aorta is the largest artery in the body, supplying blood to the abdomen, pelvis and legs.

Although it may form slowly and be asymptomatic for years, if it an AAA leaks or ruptures before it is detected and rapidly treated, the survival rate is less than 40 percent. Risk factors include emphysema, high blood pressure, male sex, obesity, high cholesterol, smoking and genetic factors.

The results of both AAA studies are reported in the Online First issue of BMJ.

Dr. S. G. Thompson, from the Institute of Public Health, Cambridge, and colleagues assessed mortality and AAA-related costs in 67,770 UK men, 65 to 74 years of age, who were randomly assigned to receive or not receive a notice for ultrasound-based AAA screening. The men found to have an AAA underwent surveillance or were offered surgery if standard operative criteria were met.

During 10 years of follow-up, 155 men in the screening group died from AAA, compared with 296 men in control group, which corresponds to rates of 0.46 percent and 0.87 percent. Thus, screening reduced the relative risk of AAA-related death by 48 percent. The survival benefit with screening was apparent early on and was maintained throughout the study period.

In the second study, Dr. Lars Ehlers, from Aarhus University, Denmark, and co-researchers used an economic decision model to assess the cost-effectiveness of ultrasound-based AAA screening in Danish men who were 65 years old.

In their model, the authors calculate that at a willingness-to-pay threshold of 30,000 pounds, the likelihood of AAA screening being cost-effective was less than 30 percent.

So why was AAA screening cost-effective in the UK study, but not in the Danish one? The reasons are not entirely clear, but in an accompanying editorial, Dr. Martin J. Buxton, from Brunel University, Uxbridge, UK, offers a possible explanation.

"Ehlers and colleagues used estimates of Danish costs that differed in important ways from the estimates in (the UK screening study) - the costs of screening are higher in Denmark compared with the UK and the differential cost between elective and emergency surgery is substantially lower. Both these factors would make screening seem less cost-effective."

SOURCE: BMJ 2009.