Ask AI



Table of contents

Antiphospholipid syndrome



APS is a systemic autoimmune disease characterized by thrombotic or obstetrical events in the presence of antiphospholipid antibodies.
APS is caused by autoantibodies targeting phospholipid-bound proteins, mainly β-2-glycoprotein I.
The prevalence of antiphospholipid antibodies in the general population is estimated at 1-5%. In the US, the estimated incidence and prevalence of APS are 5 cases per 100,000 person-years and 40-50 persons per 100,000 populations, respectively.
Disease course
The interaction of antiphopholipid autoantibodies with phospholipid-binding plasma proteins (β-2-glycoprotein I, prothrombin, thrombomodulin, kininogens, antithrombin III, annexins, protein C, and protein S) results in activation of monocytes, endothelial cells, platelets, and the complement system, inducing a prothrombotic state that leads to inflammation, vasculopathy, venous/arterial thrombosis, and obstetric complications.
Prognosis and risk of recurrence
APS is associated with morbidity related to stroke (13%), myocardial infarction (11%), DVT (9.5%), and pregnancy (6%).


Key sources

The following summarized guidelines for the evaluation and management of antiphospholipid syndrome are prepared by our editorial team based on guidelines from the European League Against Rheumatism (EULAR 2024,2022,2019), the American College of Chest Physicians (ACCP 2021), the European Society for Vascular Surgery (ESVS 2021), the American College of Rheumatology (ACR 2020), the International Society on Thrombosis and Haemostasis (ISTH ...
Show more

Screening and diagnosis

Indications for screening: as per BSH 2012 guidelines, screen women with ≥ 3 pregnancy losses before 10 weeks gestation for antiphospholipid antibodies.
Show 3 more
Create free account

Classification and risk stratification

Risk stratification: as per EULAR 2019 guidelines, stratify patients with APS into high-risk, medium-risk, and low-risk phenotypes:
Multiple antiphospholipid antibodies
Lupus anticoagulant or persistently high antiphospholipid antibody titers
History of thrombotic and/or obstetric APS
Coexistence of other systemic autoimmune diseases such as SLE
And presence of traditional cardiovascular risk factors
Anticardiolipin antibody of IgG and/or IgM isotype in serum or plasma present in titers > 40 IgG phospholipid units or > 40 IgM phospholipid units, or >the 99th percentile, measured by a standardised ELISA
Anti-β-2-glycoprotein I antibody of IgG and/or IgM isotype in serum or plasma in titer > the 99th percentile, measured by a standardised ELISA
Isolated anticardiolipin antibody or anti-β-2-glycoprotein I antibodies at low-medium titers, particularly if transiently positive

More topics in this section

  • Classification

Diagnostic investigations

Initial laboratory testing: as per BSH 2012 guidelines, obtain lupus anticoagulant testing and testing for IgG antibodies to β-2-glycoprotein I (either IgG anticardiolipin ELISA or an IgG anti-β-2-glycoprotein I ELISA). An anticardiolipin ELISA may detect antibodies to other phospholipid binding proteins as well as anti-β-2-glycoprotein I.

More topics in this section

  • Confirmatory testing

  • Non-IgG antibodies

  • Screening for portal vein thrombosis

Medical management

General principles
As per EULAR 2019 guidelines:
Screen for and manage cardiovascular risk factors appropriately in patients with antiphospholipid antibodies, including smoking cessation counseling; management of hypertension, dyslipidemia and diabetes; and promotion of regular physical activity.
Screen for and manage risk factors for venous thrombosis, and use LMWH in high-risk situations such as surgery, hospitalization, prolonged immobilisation and the puerperium.

More topics in this section

  • Management of arterial thrombosis

  • Management of VTE

  • Duration of treatment for venous thrombosis

  • Adjustment of VKAs

  • Management of recurrent thrombosis

  • DOACs

Specific circumstances

Considerations for contraception
As per ACR 2020 guidelines:
Do not use combined estrogen-progestin contraceptives in women with positive antiphospholipid antibodies because estrogen increases the risk of thromboembolism.
Offer intrauterine devices (levonorgestrel or copper) or progestin-only pills in patients with positive antiphospholipid antibodies.

More topics in this section

  • Considerations for hormone replacement therapy

  • Patients undergoing ART procedures

  • Pregnant patients

  • Pediatric patients (evaluation)

  • Pediatric patients (management)

  • Patients with catastrophic APS

Patient education

General counseling: as per EULAR 2019 guidelines, counsel patients on treatment adherence, INR monitoring in patients treated with VKA, use of perioperative bridging therapy with LMWH in patients on OACs, oral contraceptive use, pregnancy and postpartum considerations, postmenopausal hormone therapy, and general lifestyle recommendations.

Preventative measures

Primary thromboprophylaxis: as per EULAR 2024 guidelines, consider initiating low-dose aspirin (75-100 mg/day) in patients with SLE without APS but with high-risk antiphospholipid antibodies profile.