Wells-gated diagnosis with PERC and D-dimer honesty, DOAC-duration arithmetic, and filter-plus-lysis restraint

Model answer

(A) Gates with honesty (3 marks). Give Wells DVT: 593 patients with 16% prevalence; low/moderate/high carry 3/17/75% with 0.6% events in ruled-out patients — venography needed in only 5.6% with serial testing in 28%.^[1] Give duplex: proximal sensitivity 94.2% with specificity 93.8% (duplex 96.5/94.0) but distal only 63.5% (56.8% compression alone), with repeat yield 1.3%.^[3] Give PERC: all eight criteria (age under 50, pulse under 100, saturations 95%+, no haemoptysis, no oestrogen, no recent surgery/trauma admission, no prior VTE, no unilateral swelling) with 20% qualifying, 1.0% false-negatives and 97.4% sensitivity.^[5] Give the D-dimer honesty: prevalence quadruples above 4000 ng per mL, above 2000 with an unlikely score gives 36% (a likely-group number), and above 4000 prevalence is very high independent of score.^[6]

(B) Regimens with duration (4 marks). Give rivaroxaban: 15 mg twice daily for 3 weeks then 20 mg daily with 2.1 versus 3.0% (HR 0.68) and continued-treatment 1.3 versus 7.1% (HR 0.18).^[13] Give apixaban: 10 mg twice daily for 7 days then 5 mg twice daily with 2.3 versus 2.7% (RR 0.84) and major bleeding 0.6 versus 1.8%.^[15] Give dabigatran: 9-day parenteral lead-in then 150 mg twice daily with 2.4 versus 2.1% (HR 1.10).^[16] Set duration: the colectomy woman is provoked surgical disease with 4-week enoxaparin cover (12.0 versus 4.8%) then duration-limited treatment;^[8] the unprovoked woman extends — placebo recurs at 27.4% per patient-year versus 1.3% on warfarin — at conventional INR 2.0–3.0, since low intensity recurs at 1.9 versus 0.7 per 100 patient-years with identical bleeding.^[17][18]

(C) Filters with lysis pricing (3 marks). Give PREPIC: day-12 PE 1.1 versus 4.8% traded for 2-year DVT 20.8 versus 11.6% with no mortality difference.^[26] Give PREPIC2: retrievable filter plus anticoagulation gives 3-month recurrent PE 3.0 versus 1.5% (RR 2.00, ns) — no support in anticoagulable patients.^[27] Give the lapse: real-world retrieval attempted in 25.3% at median 51 days — so filter the anticoagulation-contraindicated man with a retrieval date, never as treatment.^[28] Price lysis: PEITHO prevents decompensation 2.6 versus 5.6% but strokes 2.4% with ten haemorrhagic and tied day-30 deaths;^[30] ULTIMA catheter lysis drops RV-to-LV by 0.30 versus 0.03 with no major bleeding;^[31] surgical embolectomy takes the contraindicated or shocked embolus at 6% operative mortality with 86% 1-year survival.^[33]