Safety of Abdominal Aortic Aneurysm Surveillance
What is the risk of rupture of abdominal aortic aneurysm (AAA) in men under surveillance?
Men in the National Health Service (NHS) AAA Screening Programme who initially had a small (3-4.4 cm) or medium (4.5-5.4 cm) AAA were followed-up. The screening program’s database collected data on ultrasound AAA diameter measurements and dates of referral and loss to follow-up. Local screening programs recorded adverse outcomes, including ruptured AAA (rAAA) and death. Rupture and mortality rates were calculated by initial and final known AAA diameter. Stacked cumulative incidence curves for each of the three competing events (rupture, referral for intervention, and death without rupture or referral) were produced to assess the total risk of each event during surveillance for all men combined.
A total of 18,652 men were included (50,103 men-years of surveillance). Thirty-one men had rAAA in surveillance, of whom 29 died. Some 952 men died from other causes during surveillance, mainly cardiovascular complications (26.3%) and cancer (31.2%). The overall mortality rate was 1.96% per annum, similar for men with small and medium AAA. The rAAA risk was 0.03% per annum (95% confidence interval, 0.02-0.05%) for men with small AAA, and 0.28% (0.17-0.44%) for medium AAA. The rAAA risk for men with AAA just below the referral threshold (5.0-5.4 cm) was 0.40% (0.22-0.73%).
The authors concluded that the risk of rAAA in surveillance is below 0.5% per annum, even just below the present referral threshold of 5.5 cm, and only 0.4% of men in surveillance are estimated to rupture before referral.
This study reports that the suggested referral threshold of 5.5 cm measured by ultrasound imaging results in AAA rupture rates consistently below 0.5% in men in surveillance. Overall, data suggest that current surveillance procedures in the NHS AAA screening program result in very low rupture risks. It appears that men with small and medium screen-detected AAA are safe in an intensive surveillance program, and that there is no evidence that the current referral threshold of 5.5 cm should be changed.
Keywords: Aortic Aneurysm, Abdominal, Aortic Rupture, Diagnostic Imaging, Neoplasms, Risk, Secondary Prevention, Ultrasonography, Vascular Diseases
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