Acquired bleeding disorders

Lupus anticoagulant

Topic Completed: 1 November 2012

Minor changes: 23 September 2020

Copyright: 2002-2021,, Inc.

PubMed Search: Lupus anticoagulant [title]

Jeremy C. Parsons, M.D.
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Table of Contents
Definition / general | Diagnosis
Cite this page: Parsons JC. Lupus anticoagulant. website. Accessed October 25th, 2021.
Definition / general
  • Also called lupus inhibitor
  • One of the two main types of antiphospholipid antibodies (other is anticardiolipin antibodies)
  • Common in patients with systemic lupus erythematosus, but most cases occur in patients without SLE (Arch Pathol Lab Med 2002;126:1424, Firestein: Kelley's Textbook of Rheumatology, 9th Edition, 2012)
  • May cause increased PTT (not time dependent), increased or normal PT
  • Prolongs clotting times by binding to phospholipid cofactors in coagulation cascade; often not true for HIV+ patients (Arch Pathol Lab Med 1993;117:595)

  • Indications:
    • Patients with venous thromboembolism (particularly if no family history or associated with autoimmune disease)
    • Unexplained stroke (young person or autoimmune disease), cerebral venous thrombosis, recurrent or late pregnancy loss
    • May be considered for arterial thrombosis (particularly in young patient or no documented atherosclerosis)

  • Specimen: plasma (citrate tube)
  • An algorithm combining several tests is necessary
  • All are clotting time based:
    • Russell viper venom time (sensitive to abnormalities in factors X and V, diluted for screening)
    • Kaolin clotting time
    • Dilute PT (tissue thromboplastin inhibition test)
    • PTT-based assays (should have low concentration of phospholipids to enhance sensitivity)
    • Less commonly Textarin (obtained from venomous Australian snake, not sensitive to abnormalities of factor X but sensitive to abnormalities of factor V
    • Less commonly Taipan venom (insensitive to abnormalities of factors X or V)
    • Note: all venom assays are sensitive to abnormalities in factor II, calcium and platelets
  • Use of commercially available integrated test systems is recommended:
    • Staclot procedure: add diluent to tube 1 and egg phosphatidylethanolamine to tube 2
    • Add platelet poor plasma with polybrene (neutralizes heparin) to both tubes, incubate and add PTT reagent
    • PTT in tube 2 should be 12+ seconds shorter than tube 1 to be a positive test for lupus anticoagulant
  • To demonstrate persistence, positive test must be confirmed by repeat testing after 6 - 12 weeks
  • Screening assay has low concentration of phospholipids to enhance sensitivity
    • Should have platelet count less than 10K
  • Abnormal (prolonged) PTT results may be repeated after mixing with equal amount of normal platelet-poor plasma
  • Continued prolongation of clotting time indicates an inhibitor (not a factor deficiency)
  • Confirmed by adding excess phospholipids, which should shorten clotting time towards normal
    • Must also rule out factor VIII inhibitors, heparin and other coagulopathies
  • Values prolonged by bivalirudin, lepirudin, argatroban and fondaparinux (Arch Pathol Lab Med 2004;128:1142)
  • Results vary based on dilutions in factor XII, XI, IX and VIII assays
  • May be mistaken for a factor VIII inhibitor if dilutions to abnormal factor assays are not done
  • Don’t test patients being treated with anticoagulants (or interpret with caution)
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