Background: Population screening for abdominal aortic aneurysm (AAA) has commenced in several countries, and has been shown to reduce AAA-related mortality by up to 50%. Most men who screen positive have an AAA <5.5 cm in diameter, the referral threshold for treatment, and are entered into an ultrasound surveillance program. This study aimed to determine the risk of ruptured AAA (rAAA) in men under surveillance. Methods: Men in the National Health Service 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, dates of referral, and loss to follow-up. Local screening programs recorded adverse outcomes, including rAAA and death. Rupture and mortality rates were calculated by initial and final known AAA diameter. Results: A total of 18 652 men were included (50 103 person-years of surveillance). Thirty-one men had rAAA during surveillance, of whom 29 died. Some 952 men died of 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 AAAs. The rAAA risk was 0.03% per annum (95% CI, 0.02%-0.05%) for men with small AAAs and 0.28% (0.17%-0.44%) for medium AAAs. The rAAA risk for men with AAAs just below the referral threshold (5.0-5.4 cm) was 0.40% (0.22%-0.73%). Conclusions: The risk of rAAA under surveillance is <0.5% per annum, even just below the present referral threshold of 5.5 cm, and only 0.4% of men under surveillance are estimated to rupture before referral. It can be concluded that men with small and medium screen-detected AAAs are safe provided they are enrolled in an intensive surveillance program, and that there is no evidence that the current referral threshold of 5.5 cm should be changed.
Bibliographical noteFunding Information:
This work was funded by the British Heart Foundation (RE/13/6/30180), and Homerton College, University of Cambridge. The National Health Service AAA Screening Programme, as part of Public Health England, is funded by the Department of Health.
Cardiovascular Epidemiology Unit, Department of Public Health & Primary Care, University of Cambridge, UK (C.O.-W., M.S.). Homerton College, University of Cambridge, UK (C.O.-W.). Department of Health Sciences, University of Leicester, UK (M.S.). Public Health England, Vulcan House, Sheffield, UK (J.J., L.S., A.S.). University Hospitals, Newcastle, Newcastle upon Tyne, UK (T.L.). Gloucestershire Hospitals National Health Service Foundation Trust, Cheltenham, UK.
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- Aortic aneurysm, abdominal
- Mass screening