Abdominal Aortic Aneurysm: Screening --Men aged 65 to 75 years who have never smoked


General

Grade: C

Specific Recommendations

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.

Frequency of Service

one-time screening

Risk Factor Information

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


Clinical

Practice Considerations

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 (ie, 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.13-16 Other risk factors include a history of other vascular aneurysms, coronary artery disease, cerebrovascular disease, atherosclerosis, hypercholesterolemia, and hypertension.17-19 Factors associated with a reduced risk include African American race, Hispanic ethnicity, Asian ethnicity, and diabetes.1320-24 Risk factors for AAA rupture include older age, female sex, smoking, and elevated blood pressure.1 Clinicians should consider the presence of comorbid conditions and not offering screening if patients are unable to undergo surgical intervention or have a reduced life expectancy.

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).125 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,127-31 and does not expose patients to radiation. Computed tomography is an accurate tool for identifying AAA; however, it is not recommended as a 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 (RCTs) 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 (EVAR) 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 EVAR.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 EVAR procedures (OR, 1.67 [95% CI, 1.38-2.04]) and open repair (5.37% vs 2.82%; OR, 1.76 [95% CI, 1.35-2.30]).134 Women also experience higher rates of other harms, such as major surgical complications and hospital readmission, after elective open repair or EVAR 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 EVAR.1 This recommendation is based on RCTs 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

 

Update on Previous USPSTF Recommendations

This recommendation incorporates new evidence and replaces the 2014 USPSTF recommendation.35 It is consistent with the 2014 USPSTF recommendation, which was a B recommendation for 1-time screening for AAA with ultrasonography in asymptomatic men aged 65 to 75 years who have ever smoked, a C recommendation for selective screening in men aged 65 to 75 years who have never smoked, a D recommendation against routine screening in asymptomatic women who have never smoked, and an I statement for women aged 65 to 75 years who have ever smoked.


Rationale

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.1-10 Population-based studies in men older than 60 years have found an AAA prevalence ranging from 1.2% to 3.3%.1-10 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%.111

 

 

Assessment of Magnitude of Net BenefitUSPSTF 

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 (Table).

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 (Table).

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 (Table).

The USPSTF concludes with moderate certainty that the harms of screening for AAA in women aged 65 to 75 years who have never smoked and have no family history of AAA outweigh the benefits (Table).

For more details on the methods the USPSTF uses to determine the net benefit, see the USPSTF Procedure Manual.12


Others

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