Benefit of screening for abdominal aortic aneurysm may not outweigh harms

Last Updated: 2018-06-28

By Will Boggs MD

NEW YORK (Reuters Health) - The harms of abdominal aortic aneurysm (AAA) screening of men likely outweigh the potential benefits, according to results from Swedish national registries.

"There are important harms from AAA screening. And the benefit is, at best, very small," Dr. Minna Johansson of the University of Gothenburg told Reuters Health by email. "In a health care system where referral to screening is from individual doctors (i.e., not a general-invitation system), it is important from an ethical perspective to give people information on both benefits and harms from AAA screening, to provide the opportunity to make an informed choice about participation or not."

The most recent follow-up of randomized trials conducted in the 1980s and 1990s showed a 34% relative risk reduction in AAA mortality with screening, which represented only a 0.3 percentage point reduction in absolute risk, Dr. Johansson and colleagues note in June 16 issue of The Lancet.

Since then, the incidence of AAA has decreased by more than 70%, most likely because of reduced smoking, they add. How the reduced incidence affects the benefit-to-harm balance of AAA screening remains unclear.

Dr. Johansson and colleagues estimated the effects of AAA screening on AAA mortality, the incidence and level of overdiagnosis, and the rates of surgery for AAA in Sweden, where the screening program was introduced stepwise by county between 2006 and 2015.

According to Swedish guidelines, men with an aortic diameter less than 55 mm are monitored with ultrasound at regular intervals, and preventive surgery is considered for men with an aortic diameter of 55 mm or more.

Between the early 2000s and 2015, AAA mortality decreased steadily among men aged 65-74 years (from about 36 to 10 deaths per 100,000 men) and among men aged 75-99 years (from about 90 to 60 deaths per 100,000 men). There were significant decreases beginning about 10 years before screening was introduced.

After six years of screening, AAA mortality was decreased, but only to the extent that two men per 10,000 men offered screening avoided death from AAA. This difference was nonsignificant in adjusted analyses.

The odds of having AAA diagnosed at six-year follow-up was significantly higher in the screened group than in the control group, a difference that represented 49 potentially overdiagnosed men per 10,000 men offered screening.

AAA screening was associated with an increased incidence of elective surgery for AAA that corresponded to 22 additional elective surgeries per 10,000 men offered screening.

The increase in surgery was not fully compensated for by a decrease in AAA ruptures, leaving a risk of overtreatment of 19 potentially avoidable elective surgeries per 10,000 men offered screening.

"In our opinion, the benefit of AAA screening does not seem to outweigh the harms today," Dr. Johansson said. "However, the decision to implement or deimplement screening programs is not up to individual researchers/research teams - but should be a transparent process with broad representation of different competencies - and with only people with no financial or intellectual conflicts of interests."

"We think that out study should lead to new such evaluations in the countries where AAA screening is offered," she said.

"The decreasing prevalence of smoking in Sweden (from 44% of the population in 1970, to 15% of the population in 2010) should be viewed as the main cause of the decreasing incidence and mortality of AAA," writes Dr. Stefan Acosta from Lund University, in Malmo, Sweden, in a linked editorial.

"Every percentage drop in the prevalence of smoking will have a huge effect on smoking-related diseases such as cancer and AAA. Primary prevention programs to reduce the prevalence of tobacco smoking is a top priority, whereas screening for AAA is not."

SOURCE: https://bit.ly/2tLC1cW and https://bit.ly/2Iz2CiB

Lancet 2018.