Review: Screening for abdominal aortic aneurysms in asymptomatic persons is not beneficial
ACP J Club. 1992 Jan-Feb;116:21. doi:10.7326/ACPJC-1992-116-1-021
Canadian Task Force on the Periodic Health Examination. Periodic health examination, 1991 update: 5. Screening for abdominal aortic aneurysm. Can Med Assoc J. 1991 Oct 1;145:783-9.
To evaluate and make recommendations on methods of screening for abdominal aortic aneurysms among asymptomatic persons.
MEDLINE was searched from 1981 through 1989 using the heading abdominal aortic aneurysm; from 1990 to 1991, articles were sought using aortic aneurysm and aorta, abdominal. References from pertinent articles were reviewed.
Case reports were excluded.
Data were extracted on method of screening, patient characteristics, main outcomes, and study design.
Methods of screening included physical examination, ultrasonography, abdominal radiography, aortography, computed tomography (CT), and magnetic resonance imaging. Diagnostic standards for estimation of the accuracy of these methods included surgical and autopsy findings. Estimates of prevalence were higher for men and increased with age, hypertension, claudication, smoking, and positive family history for aneurysm. Annual incidence for people > 55 years of age was reported as 22 to 499 per 100 000 men and 20 to 315 per 100 000 women, based on physical and radiologic examination, hospital admissions, and autopsy findings.
In cohort studies 65% to 90% of aneurysms in surgical patients were detected on physical examination, but in patients with smaller aneurysms, sensitivity was 22% to 96%. Specificity was 69% to 94%. Ultrasonography had a sensitivity between 82% and 99% in 8 cohort studies. It overestimated the size of the aneurysm in comparison with intraoperative measurements but was as accurate as calibrated needle measurement in estimating the anteroposterior diameter of aneurysms. Gray-scale ultrasonography was superior in definition and diagnostic accuracy to B-mode technology. Abdominal radiography, aortography, digital subtraction angiography, CT scanning, and magnetic resonance imaging are unsuitable for screening purposes because of inaccuracy, complicated procedures, or relative unavailability and cost. There were no studies addressing the question of the effect on mortality of screening for asymptomatic aneurysm; however, in several series of surgical cases, the death rate was much lower for patients having elective resection of aneurysms than for those having emergency resection of ruptured aneurysms.
The evidence for the benefit of screening asymptomatic persons for aortic aneurysm is poor and sparse; however, men at high risk may benefit from physical examination and ultrasonography.
Source of funding: Not stated.
Address for article reprint: Health Services Directorate, Health Services and Promotion Branch, Department of National Health and Welfare, Tunney's Pasture, Ottawa, Ontario K1A 1B4, Canada.
This article presents the Canadian Task Force report on screening for abdominal aortic aneurysm in the familiar pattern of an in-depth review of the literature graded by quality of studies and followed by recommendations.
The review is comprehensive and provides an effective synthesis of a large body of material. In doing so, it makes a convincing case for screening. The data presented "argue strongly for the identification and selective surgical repair of aneurysms that have not ruptured." It therefore comes as something of a surprise to find at the end of the paper that screening with physical examination or ultrasound is given a rating of "C" (poor evidence to include or exclude from the periodic health examination). Of 6 internists I asked to evaluate the article, with the recommendations deleted (do try this at home!), all graded at least 1 of the 2 screening modalities as a "B" (fair evidence to include in the periodic health examination) or higher.
Why were the Task Force recommendations conservative? The quality of the evidence appears to have been one reason. No randomized trials have examined the effect of screening on mortality from abdominal aortic aneurysm. The problem with basing recommendations on this deficiency is that such trials are probably not possible. Sudden death from ruptured abdominal aortic aneurysm would more likely be falsely attributed to some other cause in the unscreened group than in the screened group, precluding meaningful comparison (1).
The Task Force may have also had concerns about cost effectiveness, although the costs presented in the review were considered "high but not excessive." A formal economic analysis incorporating various treatment strategies would be a logical next step. Meanwhile, physicians should avail themselves of the useful review provided by the Task Force and draw their own conclusions.
Frank A. Lederle, MD
Department of Veterans Affairs Medical CenterMinneapolis, Minnesota, USA