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Should patients with antiphospholipid antibody syndrome without thrombotic or obstetric complications receive aspirin for primary prophylaxis?

Current as of 11 August 2026 · added 11 August 2026

Answer: Not routinely. The evidence is weak and of low quality, so we make a case-by-case determination based on other vascular risk factors, end-organ complications, or arterial thrombosis risk factors.

  • The 2019 EULAR recommendations do recommend low-dose aspirin (75–100 mg) for asymptomatic patients with a high-risk aPL profile — but this rests on a meta-analysis of seven observational studies.
  • The APLASA RCT found no benefit of aspirin over placebo.
  • The 2024 BSH guidance supports the case-by-case approach, favouring risk-factor modification over routine antithrombotic prophylaxis:

Recommendations

  • Routine use of LDA or hydroxychloroquine for primary prevention of thrombosis in asymptomatic aPL carriers is not recommended (2B).
  • We suggest that all individuals found to have persistently positive aPL with or without additional vascular risk factors receive thromboprophylaxis in high-risk situations such as following surgery or prolonged immobility (2C).
  • We suggest that irrespective of the aPL profile, all individuals receive advice to improve modifiable risk factors for thrombosis (1C).
  • We suggest that all asymptomatic individuals with aPL be risk assessed for cardiovascular risk factors including hypertension and hyperlipidaemia, and standard interventions including diet, lifestyle modifications and statins should be considered when these are detected (2B).

Appendix

Medium-high aPL titres. - Anticardiolipin (aCL) antibody of IgG and/or IgM isotype in serum or plasma present in titres >40 IgG phospholipid (GPL) units or >40 IgM phospholipid (MPL) units, or >the 99th percentile, measured by a standardised ELISA. Antibeta2 glycoprotein I antibody of IgG and/or IgM isotype in serum or plasma in titre >the 99th percentile, measured by a standardised ELISA.

High-risk aPL profile. - The presence (in 2 or more occasions at least 12 weeks apart) of lupus anticoagulant (measured according to ISTH guidelines), or of double (any combination of lupus anticoagulant, aCL antibodies or antibeta2 glycoprotein I antibodies) or triple (all three subtypes) aPL positivity, or the presence of persistently high aPL titres.

Low-risk aPL profile. - Isolated aCL or antibeta2 glycoprotein I antibodies at low-medium titres, particularly if transiently positive.

Related: 0011 — TPO-RAs in ITP with positive APLAs — the same aPL-driven thrombotic-risk question in a different setting.

Source: Guidelines on the investigation and management of antiphospholipid syndrome