Screening invitation, small-AAA calendar and the ruptured night — intervals, thresholds and strategy

Model answer

(A) Justify screening and state its limits (3 marks). MASS invited 67,800 men at 65 to 74 and cut AAA death 42% (65 versus 113 deaths; 53% in attenders), with elective repair at 6% against emergency at 37% — the benefit sustained at 13 years (224 versus 381, NNI 216).^[18][19] The USPSTF pool (50 studies, 323,279 participants) confirms AAA death OR 0.65, rupture OR 0.62 and emergency operations OR 0.57 — but all-cause mortality sits at RR 0.99 with 44% more procedures and no long-term quality-of-life difference, so promise fewer aneurysm deaths and fewer emergency operations, never longer life.^[20] Sweden is the contemporary anchor: 302,957 invited, 84% attend, 1.5% prevalence, 30-day death 0.9% (1.3 open, 0.3 EVAR), 667 screened and 1.5 operated per premature death prevented at EUR 7770 per QALY.^[21]

(B) Set the 4.4 cm calendar (3 marks). Survey — Cochrane's 3314-patient pool gives early repair of 4.0 to 5.5 cm no long-term advantage (pooled open HR 0.99), and CAESAR's 360 patients tie immediate EVAR against surveillance (HR 0.76 nonsignificant).^[1][2] Space scans by the ladder: around 1 year suits 4.0 to 4.9 cm per HTA, or RESCAN's rule that each 0.5 cm adds 0.59 mm per year of growth and multiplies rupture 1.91.^[4][3] Weight his modifiers — smoking accelerates growth 0.35 mm per year and doubles rupture, higher pressure raises rupture, diabetes slows growth — and repair at 5.5 cm, 1 cm per year growth, or symptoms, warning that 59.7% need repair by 36 months.^[4][2]

(C) Run the rupture night (4 marks). Activate the endovascular-first strategy where anatomy suits and the service runs around the clock: IMPROVE's 613 suspected ruptures tie at 30 days (35.4 versus 37.4%, OR 0.92) with more home discharges (94 versus 77%), then diverge mid-term to 48 versus 56% at 3 years (42 versus 54% repaired) with QALY and cost wins and tied reinterventions.^[14][16] Consent for reintervention as the norm — 186 versus 226 per 100 person-years early, 13% needing mid-term reintervention mostly for endoleak after EVAR, mandating bespoke surveillance.^[17] Name the guideline split the examiner expects: NICE runs open-first for elective AAA on old RCTs and UK modelling while ESVS runs EVAR-first on modern observational evidence — methods, not error, explain it.^[23]