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Population-wide screening of older men for abdominal aortic aneurysms resulted in increased detection and elective operations to fix the potentially deadly vessel enlargements, but screening was not associated with significantly reduced mortality during nearly 13 years of follow-up.

Secondary analysis from the randomized Western Australian Trial of Screening for Aortic Aneurysms showed no survival benefit associated with population-wide screening of older men identified from an electoral role in Australia, according to , of the Western Australian Institute for Medical Research in Perth, and colleagues, writing online in .

The U.S. Preventive Services Task Force (USPSTF) recommends for abdominal aortic aneurysms with ultrasonography in men between the ages of 65 and 75 who have ever smoked.

The findings suggest that nationwide screening programs designed to identify abdominal aneurysms involving all men over a certain age are unlikely to be effective, McCaul et al. said.

But selective screening may miss a significant percentage of abdominal aortic aneurysms (AAA) in older men, they added.

"Selective screening of smokers and ex-smokers or use of a risk scoring system might be more effective, but an earlier analysis of this cohort found that doing so would fail to identify approximately 25% of AAAs."

Initial results from the Australian trial, and three other large randomized trials examining screening for AAA in older men, showed evidence of reduced AAA-related mortality associated with screening.

The newly published long-term analysis of the Australian study included 19,249 older men invited for screening -- with 12,203 (63.4%) screened -- between April 1996 and March 1999 and 19,231 controls who were not screened. All participants were originally identified through voter registration records.

Over an average of 12.8 years of follow-up (range of 11.6 to 14.2 years), more elective operations (536 versus 414, P<0.001) and fewer ruptured AAAs (72 versus 99, P=0.04) were observed in the invited group compared with the control group.

Among the other findings:

• 90 deaths from AAAs occurred during follow-up in the invited-to-screening group (mortality rate, 47.86 per 100,000 person-years; 95% CI 38.93-58.84).
• 98 AAA-related deaths occurred in the control group (52.53 per 100,000 person-years; 95% CI 43.09-64.03) for a rate ratio of 0.91 (95% CI 0.68-1.21).
• Among men age 65 to 74, the AAA mortality rate in the invited-to-screening group was 34.52 per 100,000 person-years (95% CI 26.02-45.81) compared with 37.67 per 100,000 person-years (95% CI 28.71-49.44) in the control group, for a rate ratio of 0.92 (95% CI 0.62-1.36).
• The number needed to invite for screening to prevent one death from an AAA in 5 years was 4,784 among men between the ages of 64 and 83 and 3,290 for men age 65 to 74 years.
• There were no meaningful differences in all-cause, cardiovascular, and other mortality risks.

"Our results suggest that a national screening program using administrative databases, such as the electoral role, to identify men aged 64 to 83 years or 65 to 74 years is unlikely to be effective," the researchers wrote.

They concluded that the small, overall benefit of population-wide screening "does not mean that finding AAAs in suitable older men is not worthwhile, because deaths from AAAs in men who actually attended for screening were halved by early detection and successful treatment."

In an , titled "The Last (Randomized) Word on Screening for Abdominal Aortic Aneurysm," , of the Minneapolis VA Health Care System wrote that earlier results from the four randomized trials examining AAA screening in older men showed that screening reduced AAA-related mortality by more than 40%. This finding led to USPSTF's one-time screening recommendation for older men.

"Since then, that incorporated longer follow-up from these trials has strengthened the case for screening, revealing increasing benefit and cost-effectiveness," he wrote.

Lederle added that both the original findings and long-term follow-up from the Western Australia trial showed less benefit for AAA screening than the other trials did.

"Had the Western Australia trial been the only one conducted, AAA screening would probably never have been recommended. Two of the four trials, the Multicenter Aneurysm Screening Study () and a , have consistently found a large and statistically significant reduction in AAA-related mortality in the invited group."

Lederle noted that large decreases in the prevalence of AAAs and AAA-related deaths have been reported in epidemiological studies since the 1990s, when the participants in the four trials were recruited, "leading to continued debate on the value of screening.

"Despite the decreasing prevalence, a recent cost-effectiveness analysis (based on the MASS repair threshold of an AAA diameter of ≥5.5 cm) maintained that AAA screening remains cost-effective. This finding reflects the relatively modest contribution of screening with ultrasonography to total program cost compared with the high cost of AAA repairs."

He added that the now common practice of repairing AAAs smaller than 5.5 cm -- a practice especially prevalent in the U.S. -- dramatically lessens the benefit and cost-effectiveness of screening.

"The many small AAAs detected at screening may be serving to fill gaps in the operating schedule left by the decreasing availability of large AAA repairs," Lederle wrote. "Widespread repair of small AAAs could result in more procedural deaths caused than rupture deaths prevented. This is not the intervention that proved successful in AAA screening trials, and increases costs and harm without increasing benefit."