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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Antiphospholipid syndrome

Haematology and transfusion · UK scope · Sources checked 27 Aug 2026 · Clinical review pending

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Catastrophic antiphospholipid syndrome

Rapid thrombosis affecting three or more organs over days, often with kidney, lung, brain, skin, adrenal or cardiac injury and thrombocytopenia, is a high-mortality thrombo-inflammatory emergency.

Action: Use ABCDE and organ-specific critical care, involve haematology, rheumatology and the affected specialties immediately, obtain coagulation, haemolysis, antiphospholipid and infection samples without delaying treatment, begin therapeutic heparin when bleeding permits, give high-dose corticosteroid and arrange plasma exchange or intravenous immunoglobulin through the specialist CAPS pathway while treating infection or another trigger.

Synopsis

Confirm antiphospholipid syndrome only when a compatible clinical event and persistent antibodies coexist, select durable antithrombotic or pregnancy treatment, and recognise catastrophic APS promptly.

  • APS requires a compatible clinical event plus persistent antiphospholipid antibodies; a positive test alone is not the syndrome and should not automatically trigger anticoagulation.
  • First-line laboratory panel is lupus anticoagulant, anticardiolipin IgG and IgM and anti-beta2-glycoprotein I IgG and IgM, chosen because risk and classification differ across isolated and triple-positive profiles.
  • Confirm persistence by repeating the positive test at least 12 weeks later; acute thrombosis, inflammation and anticoagulants can distort results, especially lupus anticoagulant testing.
  • For confirmed APS after venous thrombosis, a vitamin K antagonist with usual INR target 2.0–3.0 is the standard long-term pathway after initial heparin treatment, individualised for recurrence and bleeding.
  • Do not offer a DOAC to a person with triple-positive APS under NICE VTE guidance; discuss VKA treatment with a specialist because arterial and recurrent thrombosis need tailored intensity or added antiplatelet therapy.
  • For obstetric APS without prior thrombosis, low-dose aspirin and prophylactic LMWH are commonly used from early pregnancy under maternal-fetal and haematology plans; prior thrombosis usually requires therapeutic LMWH.
  • Catastrophic APS is rapid multiorgan small-vessel thrombosis: treat the trigger and use therapeutic heparin, high-dose corticosteroid and plasma exchange or IV immunoglobulin through an expert multidisciplinary pathway.
  • Reduce modifiable thrombosis risk, avoid oestrogen-containing contraception when inappropriate, plan pregnancy before VKA exposure, and provide explicit perioperative anticoagulation and bridging instructions.

Key red flags

New hypoxaemia, kidney injury, encephalopathy, livedoid necrosis, adrenal failure or myocardial injury developing across several systems over less than a week suggests catastrophic APS rather than isolated VTE.

Pregnancy hypertension, placental insufficiency, fetal growth restriction or recurrent loss in an antibody-positive patient requires coordinated maternal-fetal and haematology assessment rather than aspirin prescribed without a plan.

A prolonged APTT caused by lupus anticoagulant does not protect against clotting and can make APTT-based unfractionated-heparin monitoring unreliable.

Catastrophic tempo

Kidney, lung, brain, skin or adrenal dysfunction developing together over days demands immediate CAPS, sepsis, TTP and DIC evaluation.

Investigation priorities

01
First-line: complete antiphospholipid antibody panelFirst stepFirst line

Identify lupus anticoagulant, anticardiolipin and anti-beta2-glycoprotein I positivity and define risk profile.

Management branches

Suspected thrombotic APSTreat clot and prove persistence

Objective venous, arterial or small-vessel thrombosis occurs with autoimmune clues, young age, unusual site or recurrence.

  1. Treat the acute event immediately and obtain a full antiphospholipid panel before anticoagulation when feasible without delay.
  2. Review infection, cancer, SLE, cardiovascular risks, medicines and hereditary factors, and arrange repeat positive antibodies after at least 12 weeks.
  3. If clinical and persistent laboratory criteria coexist, choose long-term VKA intensity and follow-up through haematology or rheumatology.

Key medicines

Warfarin after venous thrombotic APSStart with therapeutic heparin overlap and individualise oral warfarin to an INR target of 2.0–3.0 for a first venous APS event; continue long term unless specialist reassessment identifies a compelling reason to stop or change strategy.Check interactions, diet, alcohol, adherence and time in range. Warfarin is teratogenic and pregnancy requires advance LMWH transition; major bleeding needs PCC plus intravenous vitamin K and a restart plan.
Low-dose aspirin with prophylactic enoxaparin for obstetric APSUse aspirin 75–150 mg orally once daily and, when the obstetric APS plan indicates, enoxaparin 40 mg subcutaneously once daily from the specialist-defined early-pregnancy point, adjusted for weight, renal function and thrombosis history.This is not a universal regimen for antibody positivity alone. Coordinate bleeding, placenta, renal function, extremes of weight, neuraxial anaesthesia and delivery timing; prior thrombosis commonly requires therapeutic LMWH instead.
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Sources and review status5 sources · checked 27 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.

  • British Society for Haematology: investigation and management of antiphospholipid syndromeCurrent UK diagnosis, thrombotic, obstetric and catastrophic APS principles.
  • NICE NG158: venous thromboembolic diseases recommendationsUK anticoagulant choice including triple-positive APS and treatment duration.
  • NHS: antiphospholipid syndrome diagnosisNational explanation of clinical diagnosis and repeat antibody testing.
  • RCOG Green-top Guideline 37a: reducing venous thromboembolism risk in pregnancy and the puerperiumUK pregnancy risk assessment, LMWH prophylaxis and peripartum planning.
  • Clexane Summary of Product CharacteristicsLicensed enoxaparin prophylactic and therapeutic dosing and renal safety.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom