Screening for Abdominal Aortic Aneurysm: Recommendation Statement

Summary of the Recommendations The U.S. Preventive Services Task Force (USPSTF) recommends one-time screening for abdominal aortic aneurysm (AAA) by ultrasonography in men age 65 to 75 years who have ever smoked. This is a grade B recommendation. (See Appendix Table 1 for a description of the USPSTF classification of recommendations.) Appendix Table 1. U.S. Preventive Services Task Force Recommendations and Ratings The USPSTF found good evidence that screening for AAA and surgical repair of large AAAs (5.5 cm) in men age 65 to 75 years who have ever smoked (current and former smokers) leads to decreased AAA-specific mortality. There is good evidence that abdominal ultrasonography, performed in a setting with adequate quality assurance (that is, in an accredited facility with credentialed technologists), is an accurate screening test for AAA. There is also good evidence of important harms of screening and early treatment, including an increased number of surgeries with associated clinically significant morbidity and mortality, and short-term psychological harms. On the basis of the moderate magnitude of net benefit, the USPSTF concluded that the benefits of screening for AAA in men age 65 to 75 years who have ever smoked outweigh the harms. (See Appendix Table 2 for a description of the USPSTF classification of levels of evidence.) Appendix Table 2. U.S. Preventive Services Task Force Grades for Strength of Overall Evidence The USPSTF makes no recommendation for or against screening for AAA in men age 65 to 75 years who have never smoked. This is a grade C recommendation. The USPSTF found good evidence that screening for AAA in men age 65 to 75 years who have never smoked leads to decreased AAA-specific mortality. There is, however, a lower prevalence of large AAAs in men who have never smoked compared with men who have ever smoked; thus, the potential benefit from screening men who have never smoked is small. There is good evidence that screening and early treatment lead to important harms, including an increased number of surgeries with associated clinically significant morbidity and mortality, and short-term psychological harms. The USPSTF concluded that the balance between the benefits and harms of screening for AAA is too close to make a general recommendation in this population. The USPSTF recommends against routine screening for AAA in women. This is a grade D recommendation. Because of the low prevalence of large AAAs in women, the number of AAA-related deaths that can be prevented by screening this population is small. There is good evidence that screening and early treatment result in important harms, including an increased number of surgeries with associated morbidity and mortality, and psychological harms. The USPSTF concluded that the harms of screening women for AAA outweigh the benefits. Clinical Considerations The major risk factors for AAA include age (65 years), male sex, and a history of ever smoking (100 cigarettes in a person's lifetime). A first-degree family history of AAA requiring surgical repair also elevates a man's risk for AAA; this may also be true for women but the evidence is less certain. There is only a modest association between risk factors for atherosclerotic disease and AAA. Screening for AAA would most benefit those who have a reasonably high probability of having an AAA that is large enough or will become large enough to benefit from surgery. In general, adults younger than age 65 years and adults of any age who have never smoked are at low risk for AAA and are not likely to benefit from screening. Among men age 65 to 74 years, an estimated 500 who have ever smokedor 1783 who have never smokedwould need to be screened to prevent 1 AAA-related death in the next 5 years. As always, clinicians must individualize recommendations depending on a patient's risk and likelihood of benefit. For example, some clinicians may choose to discuss screening with male nonsmokers nearing age 65 who have a strong first-degree family history of AAA that required surgery. The potential benefit of screening for AAA among women age 65 to 75 years is low because of the small number of AAA-related deaths in this population. The majority of deaths from AAA rupture occur in women age 80 years or older. Because there are many competing health risks at this age, any benefit of screening for AAA would be minimal. Individualization of care, however, is still required. For example, a clinician may choose to discuss screening in the unusual circumstance in which a healthy female smoker in her early 70s has a first-degree family history for AAA that required surgery. Operative mortality for open surgical repair of an AAA is 4% to 5%, and nearly one third of patients undergoing this surgery have other important complications (for example, cardiac and pulmonary). In addition, men having this surgery are at increased risk for impotence. Endovascular repair of AAAs (EVAR) is currently being used as an alternative to open surgical repair. Although recent studies have shown a short-term mortality and morbidity benefit of EVAR compared with open surgical repair, the long-term effectiveness of EVAR to reduce AAA rupture and mortality is unknown. The long-term harms of EVAR include late conversion to open repair and aneurysmal rupture. EVAR performed with older-generation devices is reported to have an annual rate of rupture of 1% and conversion to open surgical repair of 2%. The conversion to open surgical repair is associated with a perioperative mortality of about 24%. The long-term harms of newer-generation EVAR devices are yet to be reported. For most men, age 75 years may be considered an upper age limit for screening. Patients cannot benefit from screening and subsequent surgery unless they have a reasonable life expectancy. The increased presence of comorbid conditions for people age 75 years and older decreases the likelihood that they will benefit from screening. Ultrasonography has a sensitivity of 95% and specificity of nearly 100% when performed in a setting with adequate quality assurance. The absence of quality assurance is likely to lower test accuracy. Abdominal palpation has poor accuracy and is not an adequate screening test. One-time screening to detect an AAA using ultrasonography is sufficient. There is negligible health benefit in rescreening those who have normal aortic diameter on initial screening. Open surgical repair for an AAA of at least 5.5 cm leads to an estimated 43% reduction in AAA-specific mortality in older men who undergo screening. However, there is no current evidence that screening reduces all-cause mortality in this population. In men with intermediate-sized AAAs (4.0 to 5.4 cm), periodic surveillance offers comparable mortality benefit to routine elective surgery with the benefit of fewer operations. Although there is no evidence to support the effectiveness of any intervention in those with small AAAs (3.0 to 3.9 cm), there are expert opinionbased recommendations in favor of periodic repeated ultrasonography for these patients. Discussion By definition, an AAA is present when the infrarenal aortic diameter exceeds 3.0 cm (1). Large AAAs are associated with approximately 9000 deaths annually in the United States (2). The prevalence of AAAs found in population-based ultrasonography screening studies from various countries is about 4% to 9% in men and 1% in women (3-8). The prevalence of an AAA greater than 5.0 cm in men age 50 to 79 years is estimated to be 0.5% (9). Almost all deaths from ruptured AAAs occur in men older than age 65 years, most AAA-related deaths occur in men younger than age 80 years, and most AAA-related deaths in women occur in those older than age 80 years (10, 11). The strongest risk factor for the rupture of an AAA is maximal aortic diameter (12, 13). The natural history of clinically apparent AAAs of 5.5 cm or more is difficult to determine, since most large aneurysms are surgically repaired. Results of 1 study showed that 1-year incidence rates of rupture were 9% for AAAs of 5.5 to 5.9 cm, 10% for AAAs of 6.0 to 6.9 cm, and 33% for AAAs of 7.0 cm or more (14). A rapid rate of aneurysm expansion exceeding 1.0 cm/y is commonly used in making decisions about the elective repair of AAAs less than 5.5 cm; however, the predictive value of expansion as an index of rupture risk is less clear (15). The major risk factors for AAA include male sex, a history of ever smoking (defined in surveys as 100 cigarettes in a person's lifetime), and age 65 years or older. Other lesser risk factors include family history, coronary heart disease, claudication, hypercholesterolemia, hypertension, cerebrovascular disease, and increased height (16). Factors associated with decreased risk include female sex, diabetes mellitus, and black race. Screening abdominal ultrasonography in asymptomatic individuals is an accurate test, with 95% sensitivity and near 100% specificity (17, 18). The USPSTF review identified 4 randomized, controlled trials (RCTs) of screening for AAA; these RCTs predominantly screened white men age 65 years and older (16, 18). A good-quality RCT of 67800 white men age 65 to 74 years was conducted to evaluate screening for AAA (4). Screening was performed by ultrasonography and surgery in men with AAAs greater than 5.4 cm. The study showed that AAA-related mortality was reduced by an average of 42% (95% CI, 22% to 58%) in the screened population compared with the nonscreened population; the absolute reduction in AAA-specific mortality was 0.14% (0.33% in the nonscreened group and 0.19% in the screened group) (16). A fair-quality RCT selected 15775 white men and women age 65 to 80 years from family medical practices (19). This was the only one of the 4 RCTs that studied women. The prevalence of AAA in women was one sixth of that in men. The incidence of AAA rupture was the same in the screened and control groups of women. This trial lacked adequate power an


Summary of Recommendations
The USPSTF recommends 1-time screening for abdominal aortic aneurysm (AAA) with ultrasonography in men aged 65 to 75 years who have ever smoked (Table 1). B recommendation.
The USPSTF recommends that clinicians selectively offer screening for AAA with ultrasonography in men aged 65 to 75 years who have never smoked rather than routinely screening all men in this group. Evidence indicates that the net benefit of screening all men in this group is small. In determining whether this service is appropriate in individual cases, patients and clinicians should consider the balance of benefits and harms on the basis of evidence relevant to the patient's medical history, family history, other risk factors, and personal values. C recommendation.
The USPSTF recommends against routine screening for AAA with ultrasonography in women who have never smoked and have no family history of AAA. D recommendation.
The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for AAA with ultrasonography in women aged 65 to 75 years who have ever smoked or have a family history of AAA. I statement.
See the "Practice Considerations" section for more information on each of these populations.

Importance
An AAA is typically defined as aortic enlargement with a diameter of 3.0 cm or larger. The prevalence of AAA has declined over the past 2 decades among screened men 65 years or older in various countries such as the United Kingdom, New Zealand, Sweden, and Denmark. [1][2][3][4][5][6][7][8][9][10] Population-based studies in men older than 60 years have found an AAA prevalence ranging from 1.2% to 3.3%. [1][2][3][4][5][6][7][8][9][10] The reduction in prevalence is attributed to the decrease in smoking prevalence over time. Previous prevalence rates of AAA reported in population-based screening studies ranged from 1.6% to 7.2% of the general population 60 to 65 years or older. 1 The current prevalence of AAA in the United States is unclear because of the low uptake of screening. 1 Most AAAs are asymptomatic until they rupture. Although the risk for rupture varies greatly by aneurysm size, the associated risk for death with rupture is as high as 81%. 1,11 USPSTF Assessment of Magnitude of Net Benefit The USPSTF concludes with moderate certainty that screening for AAA in men aged 65 to 75 years who have ever smoked is of moderate net benefit (Tables 1 and 2).
The USPSTF concludes with moderate certainty that screening for AAA in men aged 65 to 75 years who have never smoked is of small net benefit (Tables 1 and 2).
The USPSTF concludes that the evidence is insufficient to determine the net benefit of screening for AAA in women aged 65 to 75 years who have ever smoked or have a family history of AAA (Tables 1 and 2).
The USPSTF concludes with moderate certainty that the harms of screening for AAA in women aged 65 to 75 years who have never USPSTF smoked and have no family history of AAA outweigh the benefits (Tables 1 and 2).
For more details on the methods the USPSTF uses to determine the net benefit, see the USPSTF Procedure Manual. 12

PATIENT POPULATION UNDER CONSIDERATION
Based on the scope of the evidence review, this recommendation applies to asymptomatic adults 50 years or older. However, the randomized trial evidence focuses almost entirely on men aged 65 to 75 years. In this Recommendation Statement, the recommendations are stratified by "men" and "women," although the net benefit estimates are driven by biologic sex (i.e., male/female) rather than gender identity. Persons should consider their sex at birth to determine which recommendation best applies to them.

ASSESSMENT OF RISK
Important risk factors for AAA include older age, male sex, smoking, and having a first-degree relative with an AAA. [13][14][15][16] Other risk factors include a history of other vascular aneurysms, coronary artery disease, cerebrovascular disease, atherosclerosis, hypercholesterolemia, and hypertension. [17][18][19] Factors associated with a reduced risk include African American race, Hispanic ethnicity, Asian ethnicity, and diabetes. 13,[20][21][22][23][24] Risk factors for AAA rupture include older age, female sex, smoking, and elevated blood pressure. 1 For women aged 65 to 75 years who have ever smoked or have a family history of AAA: I statement Evidence is insufficient to assess the balance of benefits and harms of screening for AAA with ultrasonography in women aged 65 to 75 years who have ever smoked or have a family history of AAA.
To whom does this recommendation apply?

What's new?
This recommendation is consistent with the 2014 USPSTF recommendation. Family history (first-degree relative) of AAA has been added as a risk factor for screening decisions in women.
How to implement this recommendation?
Assess risk. Risk factors for AAA include older age, male sex, smoking, and having a first-degree relative with an AAA. The recommendation varies based on a patient's sex, age, and smoking history. "Ever smoker" is commonly defined as smoking 100 or more cigarettes.
Screen. Abdominal duplex ultrasonography is the standard approach for AAA screening.
Screen men aged 65 to 75 years who have ever smoked.
Selectively offer screening to men aged 65 to 75 years who have never smoked. Evidence shows that the overall benefit for screening all men in this group is small. To determine whether this service is appropriate, patients and clinicians should consider the patient's medical history, family history, other risk factors, and personal values.
For those who screen positive, treatment of AAA will depend on aneurysm size, the risk of rupture, and the risk of operative mortality.
How often?

One-time screening
What are other relevant USPSTF recommendations?
The USPSTF has made recommendations on screening for carotid artery stenosis and screening for peripheral arterial disease. These recommendations are available at http://www.uspreventive servicestaskforce.org. Smoking Status. Epidemiologic literature commonly defines an "ever smoker" as someone who has smoked 100 or more cigarettes. Indirect evidence shows that smoking is the strongest predictor of AAA prevalence, growth, and rupture rates. 1 There is a dose-response relationship, as greater smoking exposure is associated with an increased risk for AAA. 1 Family History. Family history of AAA in a first-degree relative doubles the risk of developing AAA. 25 The risk of developing an AAA is stronger with a female first-degree relative (odds ratio [OR], 4.32) than with a male first-degree relative (OR, 1.61). 1,25 However, evidence is lacking on whether persons with family history experience a different natural history or surgical outcomes than those without such a history. 1

SCREENING TESTS
The primary method of screening for AAA is conventional abdominal duplex ultrasonography. 26 Screening with ultrasonography is noninvasive, is simple to perform, has high sensitivity (94%-100%) and specificity (98%-100%) for detecting AAA, 1,27-31 and does not expose patients to radiation. Computed tomography is an accurate tool for identifying AAA; however, it is not recommended as a There is moderate certainty that screening for AAA with ultrasonography in men aged 65 to 75 years who have never smoked has a small net benefit.
The benefits and harms of screening for AAA with ultrasonography in women aged 65 to 75 years who have ever smoked or have a family history of AAA are uncertain, and the balance of benefits and harms cannot be determined.
There is moderate certainty that the harms of screening for AAA with ultrasonography in women who have never smoked and have no family history of AAA outweigh the benefits.
USPSTF screening method because of the potential for harms from radiation exposure. 1 Physical examination has been used in practice but has low sensitivity (39%-68%) and specificity (75%) and is not recommended for screening. 32

SCREENING INTERVALS
Evidence is adequate to support 1-time screening for men who have ever smoked. All of the population-based randomized clinical trials of AAA screening used a 1-time screening approach; 7 fair-to good-quality cohort studies and 1 fair-quality case-control study (n = 6785) show that AAA-associated mortality over 5 to 12 years is rare (< 3%) in men with initially normal results on ultrasonography (defined as an AAA < 3 cm in diameter). 1

TREATMENT
Treatment of AAA depends on aneurysm size, the risk of rupture, and the risk of operative mortality. Larger size is associated with an increased risk of rupture. The annual risk for rupture is nearly 0% for persons with AAAs between 3.0 and 3.9 cm in diameter, 1% for those with AAAs between 4.0 and 4.9 cm in diameter, and 11% for those with AAAs between 5.0 and 5.9 cm in diameter. 1 Surgical repair is standard practice for men with an AAA of 5.5 cm or larger in diameter or an AAA larger than 4.0 cm in diameter that has rapidly increased in size (defined as an increase of 1.0 cm in diameter over a 1-year period). Endovascular aneurysm repair has become the most common approach for elective AAA repair. Open repair is a time-tested, effective treatment for AAA. In the United States, 80% of intact AAA repairs and 52% of ruptured AAA repairs are performed using endovascular aneurysm repair. 1 The majority of screen-detected AAAs (≥ 90%) are between 3.0 and 5.5 cm in diameter and thus below the usual threshold for surgery. The current standard of care for patients with stable smaller aneurysms is to maintain ultrasound surveillance at regular intervals because the risk of rupture is small. Recommended surveillance intervals for monitoring the growth of small AAAs vary across guideline groups, and adherence with surveillance guidelines has been reported to be as low as 65%. 1 Repairing smaller aneurysms with a lower risk of rupture increases the harms and reduces the benefits of screening.

SUGGESTIONS FOR PRACTICE REGARDING THE I STATEMENT
Potential Preventable Burden. The estimated prevalence of AAA in women is reportedly less than that in men. 1 The Chichester trial reported a prevalence in women that was one-sixth of the prevalence in men (1.3% vs. 7.6%), and most AAA-related deaths occurred in women 80 years or older (70% vs. < 50% in men). 33 In women, small AAAs have an increased risk of rupture and rupture at an older age than in men. 1 Studies estimate that one-fourth to one-third of women have an AAA with a diameter below the current 5.5-cm threshold at the time of rupture. 1 Potential Harms. Operative mortality associated with AAA is higher in women than in men. Women had higher 30-day mortality rates (2.31%) than men (1.37%) after endovascular aneurysm repair procedures (OR, 1 1,34 Women also experience higher rates of other harms, such as major surgical complications and hospital readmission, after elective open repair or endovascular aneurysm repair compared with men. 1 Current Practice. Evidence is insufficient to accurately characterize current practice patterns related to screening for AAA in women. The standard of care for elective repair is that patients with an AAA of 5.5 cm or larger in diameter should be referred for surgical intervention with either open repair or endovascular aneurysm repair. 1 This recommendation is based on randomized clinical trials conducted in men. The AAA size needed for surgical intervention in women may differ. As a result, guidelines from the Society for Vascular Surgery recommend repairing AAAs between 5.0 and 5.4 cm in diameter in women. 26 However, concerns about poorer surgical outcomes in women, who have more complex anatomy and smaller blood vessels, have led some to caution against lowering the threshold for surgical intervention in women. 1 This recommendation statement was first published in JAMA. 2019; 322 (22): 2211-2218.
The "Update of Previous USPSTF Recommendation," "Supporting Evidence," "Research Needs and Gaps," and "Recommendations of Others" sections of this recommendation statement are available at https:// www.uspreventive services task force.org/Page/Document/RecommendationStatementFinal/ abdominal-aortic-aneurysm-screening1.