Putting Prevention into Practice
An Evidence-Based Approach
Screening for Abdominal Aortic Aneurysm
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Am Fam Physician. 2005 Jun 1;71(11):2154-2155.
M.G., a 70-year-old black man, requests refills for his medicines. His medications include lisinopril, atorvastatin, glipizide, and daily aspirin. He smoked heavily when he was younger but quit about 15 years ago. He also asks that you order “whatever tests should be done at my age.”
Case Study Questions
1. You review MG’s chart and find he is up to date on most age-appropriate immunizations and screening. You consider screening him for abdominal aortic aneurysm (AAA). Which of the following screening regimens reflects the U.S. Preventive Services Task Force (USPSTF) recommendations on screening for AAA?
A. Screen men and women aged 65 to 75 years.
B. Screen men yearly between the ages of 65 and 75 years.
C. Do not screen men who quit smoking more than 10 years ago.
D. Screen men aged 65 to 75 years who have ever smoked.
E. Screen women aged 75 to 85 years who have ever smoked.
2. Which one of the following statements about AAA is correct?
A. Blacks and patients with diabetes are at increased risk for AAA.
B. There is a low risk for surgical complications from AAA repair.
C. Operative mortality for open surgical repair of an AAA is less than 1 percent.
D. Men generally die from AAA rupture at an older age than women.
E. An age of 65 or older, male sex, and a history of smoking are the major risk factors for AAA.
3. After you discuss the risks and benefits of AAA screening with MG, he decides to proceed with screening. Which of the following statements about screening for AAA is/are are correct?
A. Ultrasonography is the screening test of choice.
B. An estimated 500 men aged 65 to 74 years who have ever smoked would need to be screened to prevent one AAA-related death over five years.
C. Screening and surgical repair of large AAAs in older men decreases all-cause mortality.
D. Abdominal palpation is an adequate screening alternative.
1. The correct answer is D. The USPSTF recommends one-time screening for AAA by ultrasonography in men aged 65 to 75 years who have ever smoked (defined as 100 or more cigarettes in a person’s lifetime). The USPSTF found good evidence from large population-based studies in the United Kingdom that screening for AAA and surgical repair of large AAAs lead to decreased AAA-specific mortality. Almost all deaths from ruptured AAAs occur in men older than 65 years; most AAA-related deaths occur in men younger than 80 years. For most men, 75 years may be considered an upper age limit for screening, because increased comorbidities in patients 75 years and older decrease the likelihood that they will benefit from screening. Because few AAA-related deaths occur in women, and those AAAs that do rupture occur after 80 years of age when there are competing causes of mortality, the potential benefit of screening for AAA among women is low. As always, physicians must individualize recommendations for men and women depending on a patient’s risk and likelihood of benefit. One-time screening to detect an AAA using ultrasonography is sufficient. Death from AAA rupture after negative results on a single ultrasound scan at age 65 is rare.
2. The correct answer is E. The major risk factors for AAA include an age of 65 years or older, male sex, and a history of smoking. Lesser risk factors include family history, coronary heart disease, claudication, hypercholesterolemia, hypertension, cerebrovascular disease, and increased height. Female sex, black race, and diabetes are associated with a decreased risk. In one study, the one-year incidence rate of rupture for AAAs of 5.5 to 5.9 cm (2.2 to 2.3 inches) was 9 percent. For larger AAAs, the incidence rates were higher: 10 percent for AAAs of 6.0 to 6.9 cm (2.4 to 2.7 inches) and 33 percent for AAAs 7.0 cm (2.8 inches) or greater. Major harms associated with open surgical repair of AAAs include an operative mortality of 4 to 5 percent, and approximately 32 percent of patients have other complications, including myocardial infarction, respiratory failure, renal failure, ischemic colitis, spinal cord ischemia, and prosthetic graft infections. In addition, men are at an increased risk for impotence after surgery. As discussed above, women tend to die from AAA rupture at an older age than men (mean age, 80 years).
3. The correct answers are A and B. The USP-STF found good evidence that abdominal ultrasonography is an accurate screening test for AAA. Screening abdominal ultrasonography in asymptomatic persons has 95 percent sensitivity and near 100 percent specificity when performed in a setting with adequate quality assurance. Abdominal palpation has poor accuracy and is not an adequate screening test. Among men aged 65 to 74 years who have ever smoked, the number needed to screen to prevent one AAA-related death in five years is estimated to be 500. A good-quality randomized controlled trial (RCT) and a meta-analysis of several RCTs found that open surgical repair for an AAA of at least 5.5 cm reduces the number of deaths caused by AAA from three per 1,000 to two per 1,000 in older men who undergo screening (an approximately 43 percent reduction in AAA-specific mortality). However, there is no evidence that screening reduces all-cause mortality in this population.
Fleming C, Whitlock E, Beil T, Lederle F. Primary care screening for abdominal aortic aneurysm. Evidence synthesis no. 35. Rockville, Md.: Agency for Healthcare Research and Quality, 2005. Accessed online April 22, 2005, at: http://www.ahrq.gov/clinic/uspstf05/aaascr/aaaser.pdf.
Fleming C, Whitlock EP, Beil TL, Lederle FA. Screening for abdominal aortic aneurysm: a best-evidence systematic review for the U.S. Preventative Services Task Force. Ann Intern Med. 2005;142:203–11.
Meenan RT, Fleming C, Whitlock EP, Beil TL, Smith P. Cost-effectiveness analyses of population-based screening for abdominal aortic aneurysm. Evidence synthesis. AHRQ publication no. 05–0569-C. Rockville, Md.: Agency for Healthcare Research and Quality, 2005. Accessed online April 22, 2005, at: http://www.ahrq.gov/clinic/uspstf05/aaascr/aaacost.htm.
U.S. Preventive Services Task Force. Screening for abdominal aortic aneurysm: recommendation statement. Ann Intern Med. 2005;142:198–202.
This clinical content conforms to AAFP criteria for evidence-based continuing medical education (EB CME). EB CME is clinical content presented with practice recommendations supported by evidence that has been systematically reviewed by an AAFP-approved source. The practice recommendations in this activity are available at http://www.ahrq.gov/clinic/uspstf/uspsaneu.htm.
The case study and answers to the following questions on screening for abdominal aortic aneurism are based on the recommendations of the U.S. Preventive Services Task Force (USPSTF), an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventative services. More detailed information on this subject is available in the USPSTF Recommendation Statement, the evidence synthesis, and the systematic evidence review on the USPSTF Web site (http://www.ahrq.gov/clinic/uspstfix.htm). The evidence synthesis and Recommendation Statement are available in print through the AHRQ Publications Clearinghouse (800–358–9295, e-mail, email@example.com).
This case study is part of AFP’s CME. See the “Clinical Quiz”
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