BMJ  2004;329:E311-E312 (24 July), doi:10.1136/bmj.329.7459.E311

BMJ USA: Editorial

Editorial

Screening for abdominal aortic aneurysm

Its time has come

Abdominal aortic aneurysm (AAA) has intuitively seemed an ideal candidate for detection by screening for many years. It is a common condition, especially in older men, has a long asymptomatic period of development, and is accurately detected by ultrasound. Treatment prior to rupture is certainly better than waiting till symptoms, often a fatal rupture, occur. However, routine population screening for AAA has not been recommended by major groups in the United States. In 1996 the United States Preventive Services Task Force (USPSTF) stated, "There is insufficient evidence to recommend for or against routine screening of asymptomatic adults for abdominal aortic aneurysm with abdominal palpation or ultrasound."¹

Concerns about screening for AAA expressed by the USPSTF in 1996 included the lack of randomized controlled trials with mortality outcomes, uncertainty about the natural history and management of small aneurysms, and concerns about the high surgical mortality associated with elective repair. Many of these questions have recently been answered.

The Multicentre Aneurysm Screening Study (MASS),² published in 2002, was a large randomized controlled trial of ultrasound screening for AAA in men aged 65 to 74, conducted in the United Kingdom. In this trial, death due to AAA was reduced 42% in the screened group compared to the control group. Surgical mortality was 6% after elective surgery and 37% after emergency surgery.

Two studies, the Aneurysm Detection and Management (ADAM) trial done by the Veterans Affairs Cooperative Study Group³ and the United Kingdom Small Aneurysm Trial,⁴ showed that small aneurysms can be safely followed to 55 mm in diameter before elective surgery is considered.

Thus, we now know that ultrasound screening and elective treatment can reduce deaths from AAA and that elective surgery should generally be reserved for aneurysms greater than 55 mm in diameter. Remaining questions include who should be screened, how often, and how much screening and treatment will cost.

In this issue of BMJ USA, Earnshaw et al report results of a population screening program conducted in Gloucestershire, UK, since 1990 (p 370). In their program, men were invited for a single ultrasound screening at age 65. Ninety-five percent of screenees, those with an aorta less than 26 mm in diameter, were reassured and discharged from the program. Men whose aorta measured 26 to 39 mm were followed with annual ultrasound. Men with an aortic diameter of 40 mm or more were referred for follow-up to a vascular surgery clinic. Elective surgery was considered when the aorta was greater than 55 mm in diameter. Elective surgical mortality was 4.4% in the last years of the trial.

The most cost-effective screening program for AAA would be a single ultrasound screen of male smokers or former smokers at age 60 or 65.... [A] convincing case can also be made for a single ultrasound screen for all men at age 60 or 65.

As expected, after 13 years' follow-up, mortality from AAA and the incidence of ruptured AAA have decreased substantially in Gloucestershire. The authors noted, however, that 15% of men failed to attend screening and that these men tended to have higher levels of risk than the general population. In the Gloucestershire experience, 10% of aneurysms ruptured before age 65. Screening men at age 60 instead of 65 would presumably detect most of these before rupture. The authors were concerned that if men were screened at age 60 a second screen would need to be done at age 65, doubling the cost of the program. They did not present any data to support the need for a second screen. An older study, modeling screening for AAA, suggested that repeat ultrasound screening was much more expensive, with little mortality benefit, compared to a single screen.⁵

AAA is more common in men than in women. Like many vascular diseases, it tends to occur a decade earlier in men.⁶ In the ADAM study of veterans aged 50 to 79 years, the prevalence of an aortic diameter greater than 30 mm was 4.3% for men and 1% for women. Larger aneurysms, greater than 40 mm, were 10 times more common in men than in women.⁷ One small study of screening for AAA in women did not show a mortality benefit from screening.⁶ This study was limited by its small size and compliance issues with follow-up ultrasounds and recommendations for surgery. Nonetheless, there is currently no evidence that screening for AAA is beneficial for women.

Tobacco use is the strongest risk factor for AAA. In the ADAM study, the odds ratio for an AAA greater than 40 mm in diameter was 5.57 for smokers compared to non-smokers. The excess prevalence associated with smoking accounted for 78% of all AAAs 40 mm in diameter or larger in this population.⁸ White males have twice the risk of AAA as black males. Hypertension, hyperlipidemia, and other evidence of atherosclerosis are independently associated risk factors of lesser importance. Interestingly, diabetes is negatively associated with AAA.⁸

The most cost-effective screening program for AAA would be a single ultrasound screen of male smokers or former smokers at age 60 or 65. Since accurately identifying risk factors such as smoking can be difficult and this strategy would miss the 22% of aneurysms occurring in non-smokers, a convincing case can also be made for a single ultrasound screen for all men at age 60 or 65. The Gloucestershire program shows how this can be implemented.

Insurance plans, including Medicare, should be encouraged to pay for a single screening ultrasound for men 60 years of age and older. Primary care clinicians should include a screening ultrasound for AAA in their preventive protocol for men 60 and over. This is especially important for men with a history of tobacco use. Screening ultrasounds could be done at relatively low cost by groups or practitioners with their own ultrasound capability, or patients may be referred to radiologists.

University of Rochester School of Medicine and Dentistry Rochester, NY, Tri-County Family Medicine Cohocton, NY pframe{at}stny.rr.com

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Education and debate p 370

Competing interests: None declared.

References

1. Screening for abdominal aortic aneurysm. In: U. S. Preventive Services Task Force. Guide to clinical preventive services. 2nd ed. Baltimore: Williams & Wilkins, 1996: 67-72.
2. The Multicentre Aneurysm Screening Study Group. The Multicentre Aneurysm Screening Study (MASS) into the effect of abdominal aortic aneurysm screening on mortality in men: a randomised controlled trial. Lancet 2002;360: 1531-1539.[CrossRef][ISI][Medline]
3. Lederle FA, Wilson SE, Johnson GR, Reinke DB, Littooy FN, Acher CW, et al. Immediate repair compared with surveillance of small abdominal aortic aneurysms. N Engl J Med 2002;346: 1437-1444.[Abstract/Free Full Text]
4. The United Kingdom Small Aneurysm Trial Participants. Long-term outcomes of immediate repair compared with surveillance of small abdominal aortic aneurysms. N Engl J Med 2002;346: 1445-1452.[Abstract/Free Full Text]
5. Frame PS, Fryback DG, Patterson C. Screening for abdominal aortic aneurysm in men ages 60-80 years: a cost-effectiveness analysis. Ann Intern Med 1993;119: 411-416.[Abstract/Free Full Text]
6. Scott RAP, Bridgewater SG, Ashton HA. Randomized clinical trial of screening for abdominal aortic aneurysm in women. Brit J Surg 2002;89: 283-285.[CrossRef][ISI][Medline]
7. Lederle FA, Johnson GR, Wilson SE. Abdominal aortic aneurysm in women. J Vasc Surg 2001;34: 122-126.[CrossRef][ISI][Medline]
8. Lederle FA, Johnson GR, Wilson SE, Chute EP, Littooy FN, Bandyk D, et. al. Prevalence and associations of abdominal aortic aneurysm detected through screening. Ann Intern Med 1997;126: 441-449.[Abstract/Free Full Text]

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