National screening program for AAA of little benefit in Australia

Public health

By Sunalie Silva

11 Nov 2016

A national screening program to pick up abdominal aortic aneurysm (AAA) in older men is unlikely to be effective in Australia, concede researchers in Western Australia who have completed their final analysis of a four year trial to assess screening outcomes.

While the findings from the 13-year follow up of the Western Australian trial of men aged between 64 and 83 years demonstrated an 8% reduction in mortality from AAAs, that number was considerably less than the 42% and 66% reduction seen in British and Danish trials respectively.

Some 49,801 men selected from the electoral role were randomised to a control group or a group invited to undergo ultrasonography of the abdominal aorta (n=12,200).

According to the researchers from the Harry Perkins Institute of Medical Research and the University of Western Australia, they would need to invite 4,784 men aged 64 to 83 years and 3,290 men aged 65 to 74 years for screening to prevent just one AAA-related death in 5 years.

What’s more, there were no significant differences in all-cause, cardiovascular and mortality risks, the authors said.

The lack of any perceived significant benefit was mostly put down to a lower than expected rate of rupture and death from AAAs and a high rate of elective surgery for AAAs in in the control group, the authors said.

But the authors acknowledged some people who underwent screening for the trial may have been inappropriate candidates as they were unable to exclude for prior AAA repair, major comorbidities, or advanced malignant tumours, as was done in the other trials.

The study has also raised some concerns about the harms of screening.

While the researchers did not examine nonfatal outcomes after surgery for AAAs they point out that the early morbidity of elective open surgery and the cumulative long-term complications of endovascular surgery are substantial.

“Given that screening inevitably results in a large increase in elective surgery, this unmeasured morbidity has raised questions about the underestimation of the harms of screening,” they said.

But they aren’t completely writing off the program.

“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,” they concluded.

In a linked editorial Frank A. Lederle, MD, of the Veterans Affairs Medical Center in Minneapolis said that earlier combined results from 4 trials found that screening with ultrasonography reduced AAA-related mortality in older men by more than 40%.

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

“[The Australian data] remain negative and raise some concerns about screening; [however], their aggregation with other studies does not change the overall conclusions that screening substantially reduced AAA-related mortality and also resulted in a statistically significant reduction in all-cause mortality.”

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