Older Men With Smoking History Should be Screened For Abominal Aortic Aneurysm
01/28/05 Portland, Ore.
Analysis of scientific evidence by Oregon researchers guides U.S. Preventive Services Task Force decision to not recommend screening for all men and women older than 65
The Task Force, an independent panel of experts sponsored by the Agency for Healthcare Research and Quality, based its recommendations on a report from a team led by Craig Fleming, M.D., of the Oregon Evidence-Based Practice Center, a consortium of clinicians and researchers from Oregon Health & Science University, Kaiser Permanente Center for Health Research, and the Portland Veterans Affairs Medical Center. The findings, which are published in the Feb. 1 issue of the Annals of Internal Medicine, mark the first time the Task Force has recommended screening for AAA.
The Task Force made no recommendation for or against screening for AAA in men in the same age group who have never smoked. It recommended against routine screening for AAA in women. Few studies have been conducted in women and published research indicates women are at low risk for aneurysms.
Abdominal aortic aneurysm (AAA) happens when the aorta below the renal artery expands to a diameter of 3.0 cm or greater. AAAs occur in 4 percent to 8 percent of older men and in 0.5 percent to 1.5 percent of older women. The most significant risk factors for AAA are age, sex, smoking status and family history. Nearly 9,000 Americans die every year from AAAs that rupture, and most of these deaths occur in men aged 65 and older. Because most people die before getting to the hospital or before surgery, and the death rate for emergency AAA surgery is high, only 10 percent to 25 percent of patients with ruptured AAAs survive until hospital discharge.
This high mortality rate raises important questions about screening asymptomatic populations that are at average or high risk for AAA: Does screening reduce AAA-related deaths or other negative outcomes, should screening be one-time or periodic, does screening cause harm, and does repair of unruptured AAAs cause harm? To provide the Task Force with answers to these questions, Dr. Fleming and colleagues systematically reviewed all relevant scientific studies published between 1994 and 2004; identified four randomized, controlled trials of population-based screening for AAA; and analyzed results from these trials as well as other AAA-related studies.
"What we found," said Fleming, clinical investigator at Kaiser Permanente's Center for Health Research, "is that men aged 65 or older who were invited to receive screening had a 43 percent lower death rate, after five years, than men who did not receive a screening invitation. Only one study examined AAA screening in women, and it showed there was no difference in AAA-related mortality after five years between women who did and did not receive a screening invitation. Using accepted modeling techniques, we also found that sending a screening invitation only to the 69 percent of American men who are 65 to 74 years of age and have a history of smoking, which we defined as more than 100 cigarettes in their lifetime, would account for an 89 percent reduction in AAA-related deaths if all men aged 65 to 74 received a screening invitation."
Fleming and his colleagues also found that repeated screening up to 10 years after a first negative screening by ultrasonography of men aged 65 failed to find significant new aneurysms. They also found that ultrasonography, a non-invasive screening test lasting 10 minutes, had no physical or psychological harms. Finally, they found that the in-hospital death rate for elective (unruptured) AAA repair varied from 2 percent to 6 percent, and about one in three patients experienced serious complications such as a heart attack following surgery. The risk for death and complications increased with age, and death rates for AAA repair were lower when performed by experienced vascular surgeons in hospitals where the procedure is frequently done.
The Oregon EPC provides evidence reviews for the U.S. Preventive Services Task Force, an independent panel of private-sector experts in prevention and primary care that conducts rigorous, impartial assessments of the scientific evidence for a broad range of preventive services. Its recommendations are considered the gold standard for clinical preventive services.