Background: Because many abdominal aortic aneurysms (AAAs) go undiagnosed until they rupture, several recent studies have examined the role of screening in reducing AAA-related mortality. Although these reports consistently show reduced short-term mortality, no data have demonstrated a longer-term survival benefit. Potential screening programs must balance a long-term benefit with cost-effectiveness; however, the long-term cost-effectiveness of these screening programs has only been estimated through economic modeling. Kim and colleagues evaluated midterm results of the Multicentre Aneurysm Screening Study (MASS) for changes in mortality and cost-effectiveness.
The Study: The MASS trial, one of the largest AAA screening studies, followed 67,770 men 65 to 74 years of age in the United Kingdom who were randomly assigned to be invited or not invited to receive screening ultrasonography. The study recruited patients between 1997 and 1999 and excluded those with known AAA, a previous AAA surgery, or a terminal illness. At screening, an aortic diameter less than 3 cm was considered normal, and no further screening was offered. All men with an aortic diameter of at least 3 cm and who were diagnosed with AAA were recalled for surveillance scanning and rescreened based on initial aortic diameter. Those with an aortic diameter of at least 5.5 cm and with an aortic aneurysm expansion greater than 1 cm in a year or with symptoms related to AAA were offered elective surgery. Outcomes were collected via each patient's National Health Service number. In addition, AAA-related deaths in both groups were evaluated.
Results: Initial results were published at four years and showed a decrease in AAA-related deaths in the group invited for screening. The results also showed borderline cost-effectiveness. This study reported outcome data at a mean of 7.1 years (range of 5.9 to 8.2 years) after screening. The decreased AAA-related mortality rate (the risk was halved in the invited group) was maintained at four and seven years. In addition, all-cause mortality decreased in the invited group at seven years, reflecting a concomitant decrease in ischemic heart disease deaths, perhaps because of positive lifestyle changes.
Cost-effectiveness continued to improve at seven years, as the initial costs associated with screening and elective repair remained fairly constant and the costs associated with emergent repairs decreased, with reduced numbers of surgeries in the invited group. At seven years, the cost-effectiveness is estimated to be approximately $19,500 per life-year gained, which compares favorably with other screening programs.
Conclusion: This midterm evaluation of the MASS trial continues to support the use of one-time screening for AAA in men 65 to 74 years of age based on cost-effectiveness and reduced mortality. The authors do caution that the cost-effectiveness data were derived from a general screening population and not from a selective screening of higher-risk groups (e.g., smokers).
editor's note: The U.S. Preventive Services Task Force only recommends AAA screening for men 65 to 75 years of age if they have ever smoked.1—a.c.f.