By Erik L. Ridley, AuntMinnie staff writer

January 28, 2014 -- In an update on Monday to its 2005 recommendations for ultrasound screening for abdominal aortic aneurysms (AAA), the U.S. Preventive Services Task Force (USPSTF) largely kept to its previous recommendations for men while adding nuance to its suggestions for screening in women.

In its new draft recommendation statement, USPSTF retained its B-grade recommendation for one-time ultrasound screening for AAA in men 65 to 75 who have ever smoked. In keeping with a change to the definition of its C grade level, USPSTF now suggests selective screening for men of this age group who have never smoked. In 2005, the same C grade level indicated that the task force made no recommendation for or against screening.

The task force modified its recommendations for ultrasound screening for AAA in women, providing separate guidance for women who have smoked and those who haven't. While in 2005 USPSTF recommended against screening in all women, the task force has now concluded that current evidence is insufficient to assess the balance of benefits and harms of ultrasound screening in women 65 to 75 who have ever smoked. It continues to recommend against screening in women who have never smoked.

The new draft recommendations were based on a systematic evidence review of the benefits and harms of ultrasound screening for AAA in asymptomatic individuals. Four population-based, randomized, controlled trials were included: the Multicenter Aneurysm Screening Study (MASS); a screening trial in Viborg County, Denmark; the Western Australia trial; and the Chichester, U.K., screening trial.

The four trials showed that a one-time invitation for AAA screening in men 65 and older reduced AAA rupture for up to 10 years and AAA-related mortality for up to 15 years, according to the review, which was published online January 27 in the Annals of Internal Medicine. However, ultrasound screening was not found to yield a statistically significant effect on all-cause mortality rates up to 15 years.

The review also found that screening was associated with more overall and elective surgeries, but also fewer emergency operations and lower 30-day operative mortality rates at up to 10- to 15-year follow-up. Furthermore, the one study that included women (the Chichester trial) failed to show a benefit of screening on AAA-related or all-cause mortality rates, according to the group.

Recommendations for men

In its updated recommendations, the task force retained its grade B recommendation for one-time ultrasound screening for AAA in men 65 to 75 who have ever smoked. The B grade indicates a high certainty that the net benefit is moderate or moderate certainty that the net benefit is moderate to substantial.

"There is convincing evidence that one-time screening for AAA with ultrasonography results in a moderate benefit in men ages 65 to 75 years who have ever smoked," the group wrote in the recommendation statement.

In addition, the task force continued its grade C recommendation for screening in men ages 65 to 75 who have never smoked. However, USPSTF has changed the meaning of the C grade since the 2005 update. In 2005, the C grade indicated that the task force made no recommendation for or against screening in this group. The C grade now indicates that USPSTF recommends selectively offering or providing the service to individual patients based on professional judgment and patient services, as there is at least moderate certainty that the net benefit is small.

"Despite the demonstrated benefits of screening for AAA in men overall, the much lower prevalence of disease in male never-smokers than in male ever-smokers suggests that clinicians should consider the patient's risk factors as well as the potential for causing harm when making the decision whether to screen, instead of routinely offering screening to all men who have never smoked," the group stated in the recommendations.

The task force went on to note that important risk factors that increase the risk of developing an AAA include older age and a first-degree relative with AAA. Other risk factors include a history of other vascular aneurysms, coronary artery disease, cerebrovascular disease, atherosclerosis, hypercholesterolemia, obesity, and hypertension. In addition, African-American race, Hispanic ethnicity, and diabetes are associated with a reduced risk of developing an AAA.

A change for women

In 2005, USPSTF gave a D grade to ultrasound screening for AAA in women, reflecting its recommendation to discourage its use. However, the task force has now provided a separate statement for its recommendation for women ages 65 to 75 who have ever smoked; USPSTF has concluded that evidence is lacking, of poor quality, or conflicting, and the balance of benefits and harms cannot be determined in this patient group.

"While there is evidence that women who smoke are at increased risk for AAA compared with their nonsmoking counterparts, there is insufficient evidence that screening confers a net benefit," the task force wrote. "Appropriately powered [randomized, controlled trials] as well as high-quality modeling studies should be done to determine whether screening is beneficial in women who smoke. The same is true for persons with a family history of AAA and those with combinations of risk factors."

The group noted that AAA screening is provided as part of the "Welcome to Medicare visit" to women who have a family history of AAA, but there is insufficient evidence to accurately characterize current clinician practice patterns related to AAA screening in women.

USPSTF continues to recommend against routine AAA screening in women who have never smoked.

"The USPSTF found adequate evidence that screening for AAA in women who have never smoked provides an AAA-specific mortality benefit that can effectively be bounded at zero," the task force wrote. "Adequate evidence indicates that the harms of AAA screening in this population are at least small, and may be higher than in men due to higher rates of operative mortality. The USPSTF concludes with moderate certainty that screening for AAA in women ages 65 to 75 years who have never smoked is of no net benefit."

The draft recommendation statement is available for review and public comment until February 24 and can be accessed here.


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