New USPSTF AAA Screening Advice: Can We Do More?

Patrice Wendling

December 17, 2019

The 2019 US Preventive Service Task Force (USPSTF) recommendations for abdominal aortic aneurysm (AAA) screening are largely unchanged from the 2014 iteration — and therein lies the rub.

The updated statement, published recently in the Journal of the American Medical Association, points to a paucity of contemporary randomized controlled trials (RCTs) to support expanding AAA screening to key populations — women with a history of smoking, individuals older than 75, and nonsmokers with other equivalent risk factors.

Accompanying editorials, however, note that screening entails a simple, onetime, noninvasive ultrasonography exam that costs roughly $50 and that other regulatory and government bodies currently support broader use of screening.

As it stands, the updated recommendations for asymptomatic adults are:

  • For onetime screening with ultrasonography in men aged 65 to 75 years who have ever smoked (grade B)

  • For selective screening for men aged 65 to 75 who never smoked (grade C)

  • Against routine screening in women aged 65 to 75 who never smoked and have no family history of AAA (grade D)

  • Insufficient evidence to recommend either for or against screening in women aged 65 to 75 who ever smoked or have a family history of AAA (I statement)

The biggest change from 2014 was moving family history of AAA into the grade "I statement" to ensure that the D recommendation against screening in nonsmokers was for very low-risk women, USPSTF member Chyke Doubeni, MD, MPH, Mayo Clinic, Rochester, Minnesota, told | Medscape Cardiology.

He noted that the recommendations are largely based on four RCTs reported in the early 2000s comparing early surgical intervention with surveillance of smaller aneurysms. All were underpowered to detect differences in subpopulations and only one trial included women.

In addition, AAAs in women tend to rupture at a later age and at a smaller size than in men, he noted. Surgical outcomes also may not be as good in women as in men.

"If you put all those things together, we just don't have strong enough evidence to make the same recommendation that we made for men," Doubeni said. "Clearly we need more research in this area."

The task force also had to weigh the potential harms of screening, a concern raised when a draft of the document was posted for public comment this summer. In response, they added information about overtreatment to the Supporting Evidence section and information about comorbid conditions to the Practice Considerations section.

In a linked editorial, Matthew Mell, MD, MS, division of vascular surgery, University of California Davis in Sacramento, acknowledges that differences in aneurysm size at rupture between sexes, a lower prevalence of AAA in women, and a higher mortality with elective repair complicate the decision-making process.

However, he notes these "challenges" have led the Society for Vascular Surgery to recommend more liberal use of screening, including onetime ultrasonographic screening in men and women aged 65 to 75 with a history of tobacco use, men 55 years or older with a family history of AAA, and women aged 65 years with a family history of AAA.

"Women with a significant smoking history may have a prevalence of AAA exceeding 2%; therefore, it is reasonable to screen this cohort for AAA and consider repair for an AAA greater than 5.0 to 5.5 cm in diameter," Mell reported in JAMA Network Open.

In a second editorial published in JAMA Surgery, Marc Schermerhorn, MD, division of vascular surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, writes that "overreliance on outdated screening trials is problematic" as the advent of endovascular aortic repair (EVAR) has "changed the paradigm of AAA management."

Though women tend to develop AAA at a later age and have a higher operative mortality with repair, they live longer, he notes. Additionally, the sex gap in terms of perioperative morbidity with repair is narrowing, likely due to technological advances in EVAR with lower-profile, more flexible devices.

Recent work also suggests female smokers have a prevalence of AAA of 1.7%, and the effect of other risk factors is additive. This is noteworthy, as the draft of the upcoming National Institute for Health Care and Excellence (NICE) guidelines determined that screening is cost effective if the prevalence of AAA is greater than 0.35%.

"These data appear not to have been considered by the USPSTF, perhaps owing to the lack of modern randomized clinical trials that are unlikely to be repeated given the great expense and the limited government funding for such endeavors," Schermerhorn said.

The draft NICE guidelines support "more broad coverage for screening that may make more sense," he suggested. The cutoff of greater than 0.35% would include men and women with more than one risk factor including male sex, age older than 65 years, smoking, hypertension, chronic obstructive pulmonary disease, atherosclerotic cardiovascular disease, and family history of AAA.

The safety of EVAR in elderly patients is a key factor in screening considerations, Schermerhorn said. Individuals older than 75 years have the highest rates of AAA and of rupture, but are increasingly underdoing EVAR with a reported operative mortality rate of only 1.4%.

Expanding screening to these individuals would also "avoid punishing patients whose clinicians failed to screen them during the covered age range," he said.

The US Centers for Medicare & Medicaid Services (CMS) already fund screening for men and women aged 65 to 75 years with a family history of AAA regardless of smoking status, despite USPSTF recommendations.

Recent estimates, however, suggest only 15% of eligible CMS beneficiaries are screened. For these reasons, the draft NICE guidelines do not have an upper age cutoff for screening, Schermerhorn observed.

"It would appear more prudent to base this decision on life expectancy and predicted operative risk with EVAR (both of which can be calculated with predictive models), rather than a cutoff of age 75 years that might appear arbitrary or even discriminatory as life expectancy in the United States continues to increase," he said.

Commenting further, he added, "We as a country can do better to detect and treat this disease cost effectively for all appropriate patients including women and elderly individuals."

The task force noted that the American College of Cardiology and American Heart Association jointly recommend onetime screening for AAA with physical examination and ultrasonography in men aged 65 to 75 years who have smoked or in men 60 years or older who are the sibling or offspring of a person with AAA. They do not recommend screening in men who have never smoked or in women.

The American College of Preventive Medicine also does not recommend routine screening in women, but recommends onetime screening in men aged 65 to 75 years who have ever smoked.

Doubeni expressed frustration at the lack of new evidence, including data in another subgroup — racial minorities who tend to have different characteristics and risks for AAA. Still, while epidemiological and observational data provide context, the USPSTF bases its recommendations on reliable research that show the benefits and harms of screening, he said.

The task force highlighted several research gaps, among them, the need for:

  • Appropriately powered RCTs among women with risk factors for AAA to determine if screening confers a net benefit

  • Well-designed studies, RCTs, or registry data on the thresholds for repair of AAA in women

  • External validation of risk-prediction models

  • Epidemiologic studies on the current prevalence of AAA in the United States

  • Studies examining systems approaches to improving evidence-based AAA screening

  • Well-conducted cohort studies examining rescreening benefits

  • Studies examining the efficacy of screening and treatment in diverse populations, such as older adults and racial/ethnic groups

AAA expert Julie Ann Freischlag, from Wake Forest Baptist Medical Center, Winston-Salem, North Carolina, highlighted similar research needs in a third related editorial, which was published in JAMA.

"Precision screening recommendations are possible," she said. "But more information is needed about the prevalence and growth rates of AAA in men and women with diverse backgrounds so that care — including screening, follow-up, and treatment — can be individualized, and outcomes for patients with AAA can be improved."

USPSTF co-author Michael Barry, MD, reported grants and personal fees from Healthwise; all other authors have disclosed no relevant financial relationships. Schermerhorn has consulting arrangements with Abbott, Cook Medical, Endologix, Medtronic, and Philips. Mell and have disclosed no relevant financial relationships.

JAMA. 2019;322:2211-2218, 2177-2178. Full text, Editorial

JAMA Netw Open. 2019;2:e1917168. Editorial

JAMA Surg. Published online December 10, 2019. Editorial

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