Anticoagulation in Antiphospholipid Syndrome

Introduction to Anticoagulation

The American College of Chest Physicians recommends adjusted-dose vitamin K antagonist (VKA) over direct oral anticoagulants (DOACs) during the treatment phase for patients with confirmed antiphospholipid syndrome (APS) and thrombosis 1
Anticoagulation should be initiated in APS-positive patients who have experienced a thrombotic event, while asymptomatic patients with positive antibodies alone do not require anticoagulation 2

Patients who meet full diagnostic criteria for APS and have had a documented thrombotic event require anticoagulation, including both venous thromboembolism and arterial thrombosis 2, 3, 4, 5
Asymptomatic antibody-positive patients do not require anticoagulation, but may be considered for low-dose aspirin therapy 3, 4, 5

Vitamin K antagonist (warfarin) with target INR 2.5 (range 2.0-3.0) is the first-line therapy for patients with confirmed APS and thrombosis 2, 1, 6
For venous thrombosis, warfarin with target INR 2.0-3.0 is recommended 2
For arterial thrombosis, warfarin with target INR 2.0-3.0 or 3.0-4.0 may be considered based on individual bleeding and recurrence risk 2

Direct oral anticoagulants (DOACs) are contraindicated in triple-positive APS patients due to increased risk of recurrent thrombosis compared to warfarin 2, 6
Estrogen-containing contraceptives are strongly contraindicated in women with positive antiphospholipid antibodies due to significantly increased thrombosis risk 2
In pregnancy, use low molecular weight heparin plus low-dose aspirin throughout pregnancy, not warfarin, which is teratogenic in the first trimester 2, 6
For cerebral venous thrombosis, initiate anticoagulation immediately with low molecular weight heparin (LMWH) or unfractionated heparin, then transition to warfarin targeting INR 2.0-3.0 6
For treatment-refractory APS, consider adding antiplatelet therapy to anticoagulation, and hydroxychloroquine may be added, especially in patients with underlying systemic lupus erythematosus 2, 6

If thrombosis recurs with INR in therapeutic range (2.0-3.0), increase target to INR 2.5-3.5, as recommended by Circulation 7

Bridge with therapeutic-dose low molecular weight heparin (LMWH) or unfractionated heparin while initiating warfarin on day 1-2, overlapping until INR is therapeutic (≥2.0) for at least 24 hours, as recommended by the American College of Chest Physicians 8

Estrogen-containing contraceptives (OCPs) are absolutely contraindicated permanently in APLA-positive patients, and safe contraceptive alternatives include progestin-only methods, copper IUD, or barrier methods, according to the American College of Rheumatology 9
Depot medroxyprogesterone acetate (DMPA) is generally safe but should be avoided if the patient has osteoporosis risk, as suggested by the American College of Rheumatology 9

If the patient becomes pregnant in the future, immediately switch from warfarin to therapeutic-dose LMWH plus low-dose aspirin (75-100 mg daily) throughout pregnancy and for 6-12 weeks postpartum, as recommended by the American College of Rheumatology 10 and the American College of Chest Physicians 8
For thrombotic APS in pregnancy, therapeutic-dose LMWH (not prophylactic dose) plus aspirin is required, according to the American College of Rheumatology 10

Consider adding hydroxychloroquine 200-400 mg daily, particularly if the patient has underlying systemic lupus erythematosus or recurrent thrombosis despite therapeutic anticoagulation, as suggested by the American College of Rheumatology 10
Hydroxychloroquine may reduce thrombotic complications in APS, according to the American College of Rheumatology 10

Reconfirm APLA positivity with repeat testing at least 12 weeks after initial positive test to meet diagnostic criteria, as recommended by the American College of Rheumatology 9