antiphospholipid antibodies

Last edited 04/2019 and last reviewed 04/2019

Antiphospholipid antibodies (APAs) are a heterogenous group of antibodies directed against plasma proteins which bind to phospholipids.

  • seen in 1-5% of apparently healthy subjects
  • increased prevalence is seen with age and may be influenced by chronic disease, infections, malignancies and certain drugs
  • it can arise as a primary phenomenon or secondary to other disorders such as connective tissue disorders, infections and malignancy (2)
  • types of antiphospholipid antibodies include
    • lupus anticoagulant
      • the specificity for thrombosis is higher for LA than aCL or anti–β2-glycoprotein I antibodies (anti- β2GPI)
      • also it is greater for higher than lower titre aCL
    • anti–β2-glycoprotein I antibodies (anti- β2GPI)
    • anticardiolipin antibodies (1)
  • appropriate laboratory tests considered for detection of APAs include:
    • lupus-anticoagulant assays -
      • a functional assay based on a combination of several clotting tests
      • detects immunoglobulins that cause prolonged clotting times in vitro but are associated with thrombosis in vivo
      • some commonly used tests are the activated partial thromboplastin time (aPTT), the dilute Russell's viper venom time (dRVVT), and the kaolin clotting time (KCT).
    • cardiolipin ELISA - detects antibodies against cardiolipin and cardiolipin bound β2-glycoprotein I
    • anti– β2-glycoprotein I ELISA - antibodies against β2-glycoprotein I
  • in patients who have all three tests positive, there is a higher risk for pregnancy morbidity or thromboembolism