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Screening for abdominal aortic aneurysms did not reduce mortality

Mortality related to abdominal aortic aneurysms was not significantly reduced in older men who underwent screening compared with those who did not, according to a secondary analysis of the Western Australian trial published in JAMA Internal Medicine.

“The initial reports of four large randomized clinical trials of screening for abdominal aortic aneurysm (AAA) in men 65 years or older indicated that screening reduces mortality from AAAs,” Kieran A. McCaul, PhD, from the Western Australian Institute for Medical Research. “Although results [from the Western Australian trial] after 43 months of follow-up demonstrated a relative risk reduction of 39%, this finding was not statistically significant, and long-term results to enable comparison with the [Multicentre Aneurysm Screening Study (MASS) in the United Kingdom] and Danish trials have not been reported.”

Between April 1, 1996 and March 31, 1999, McCaul and colleagues conducted a population-based randomized clinical trial to investigate if screening for AAAs in older men reduced AAA-related mortality. Men aged 64 to 83 years from a metropolitan region in Western Australia (n = 49,801; mean age, 72.5 years; 95% white) were identified by the electoral roll and enrolled in the study. Follow-up was conducted between 11.6 and 14.2 years (mean, 12.8 years). The researchers analyzed the data from June 1, 2015 to June 1, 2016.

Participants were randomly assigned to a control group (n = 19,231) or a group invited to undergo ultrasonography of the abdominal aorta (n = 19,249). Of those invited for screening, 12,203 (63.4%) attended.

Compared with the control group, the invited group had more elective operations (536 vs. 414, P < .001) and fewer ruptured AAAs (72 vs. 99, P = .04). There was no significant difference in the number of AAA-related deaths between the invited group (n = 90; mortality rate, 47.86 per 100,000 person-years [95% CI, 38.93-58.84]) and the control group (n = 98; mortality rate, 52.53 per 100 000 person-years [95% CI, 43.09-64.03]). The respective rate ratio was 0.91 (95%CI, 0.68-1.21).

Men aged 65 to 74 years had an AAA mortality rate of 34.52 per 100,000 person-years (95% CI, 26.02-45.81) in the invited group and 37.67 per 100,000 person-years (95% CI, 28.71-49.44) and the control group, with a rate ratio of 0.92 (95% CI, 0.62-1.36).

The researchers reported that 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. In addition, they did not observe significant differences in all-cause, cardiovascular and mortality risks.

“Our results suggest that a national screening program using administrative databases ... is unlikely to be effective,” McCaul and colleagues concluded. “Differences in health care systems ... may influence the benefit of screening for AAAs and should be considered in individual countries before the introduction of screening. 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 a related editorial, Frank A. Lederle, MD, of the Veterans Affairs Medical Center in Minneapolis, wrote that the findings from the Western Australian trial conflict with previous studies on screening for AAAs in older men and therefore, will mainly result in updating meta-analyses.

“[These 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.” – by Alaina Tedesco

Disclosure: McCaul and colleagues report receiving grants from the National Health and Medical Research Council Project. Lederle report no relevant financial disclosures.