• Simon G Thompson, Matthew J Bown, Matthew J Glover, Edmund Jones, Katya L Masconi, Jonathan A Michaels, Janet T Powell, Pinar Ulug, and Michael J Sweeting.
• Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK.
• Health Technol Assess. 2018 Aug 1; 22 (43): 1-142.

BackgroundAbdominal aortic aneurysm (AAA) screening programmes have been established for men in the UK to reduce deaths from AAA rupture. Whether or not screening should be extended to women is uncertain.ObjectiveTo evaluate the cost-effectiveness of population screening for AAAs in women and compare a range of screening options.DesignA discrete event simulation (DES) model was developed to provide a clinically realistic model of screening, surveillance, and elective and emergency AAA repair operations. Input parameters specifically for women were employed. The model was run for 10 million women, with parameter uncertainty addressed by probabilistic and deterministic sensitivity analyses.SettingPopulation screening in the UK.ParticipantsWomen aged ≥ 65 years, followed up to the age of 95 years.InterventionsInvitation to ultrasound screening, followed by surveillance for small AAAs and elective surgical repair for large AAAs.Main Outcome MeasuresNumber of operations undertaken, AAA-related mortality, quality-adjusted life-years (QALYs), NHS costs and cost-effectiveness with annual discounting.Data SourcesAAA surveillance data, National Vascular Registry, Hospital Episode Statistics, trials of elective and emergency AAA surgery, and the NHS Abdominal Aortic Aneurysm Screening Programme (NAAASP).Review MethodsSystematic reviews of AAA prevalence and, for elective operations, suitability for endovascular aneurysm repair, non-intervention rates, operative mortality and literature reviews for other parameters.ResultsThe prevalence of AAAs (aortic diameter of ≥ 3.0 cm) was estimated as 0.43% in women aged 65 years and 1.15% at age 75 years. The corresponding attendance rates following invitation to screening were estimated as 73% and 62%, respectively. The base-case model adopted the same age at screening (65 years), definition of an AAA (diameter of ≥ 3.0 cm), surveillance intervals (1 year for AAAs with diameter of 3.0-4.4 cm, 3 months for AAAs with diameter of 4.5-5.4 cm) and AAA diameter for consideration of surgery (5.5 cm) as in NAAASP for men. Per woman invited to screening, the estimated gain in QALYs was 0.00110, and the incremental cost was £33.99. This gave an incremental cost-effectiveness ratio (ICER) of £31,000 per QALY gained. The corresponding incremental net monetary benefit at a threshold of £20,000 per QALY gained was -£12.03 (95% uncertainty interval -£27.88 to £22.12). Almost no sensitivity analyses brought the ICER below £20,000 per QALY gained; an exception was doubling the AAA prevalence to 0.86%, which resulted in an ICER of £13,000. Alternative screening options (increasing the screening age to 70 years, lowering the threshold for considering surgery to diameters of 5.0 cm or 4.5 cm, lowering the diameter defining an AAA in women to 2.5 cm and lengthening the surveillance intervals for the smallest AAAs) did not bring the ICER below £20,000 per QALY gained when considered either singly or in combination.LimitationsThe model for women was not directly validated against empirical data. Some parameters were poorly estimated, potentially lacking relevance or unavailable for women.ConclusionThe accepted criteria for a population-based AAA screening programme in women are not currently met.Future WorkA large-scale study is needed of the exact aortic size distribution for women screened at relevant ages. The DES model can be adapted to evaluate screening options in men.Study RegistrationThis study is registered as PROSPERO CRD42015020444 and CRD42016043227.FundingThe National Institute for Health Research Health Technology Assessment programme.

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