Coagulation
Acquired bleeding disorders
Lupus anticoagulation & antiphospholipid antibodies
Author: Jeremy C. Parsons, M.D.
Last author update: 1 November 2012
Last staff update: 4 March 2022
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: Lupus anticoagulant [title]
Cite this page: Parsons JC. Lupus anticoagulation & antiphospholipid antibodies. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/coagulationlupusanticoag.html. Accessed December 4th, 2024.
Definition / general
- Also called lupus inhibitor
- One of the 2 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)
Diagnosis
- 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)
Antiphospholipid antibodies
- Acquired antibodies against phospholipid protein complexes
- Occurs in 3 - 5% of general population; most common cause of acquired thrombophilia
- Rate of thrombosis per year is 1% if no history of thrombosis, 4% in systemic lupus erythematosus (SLE) patients, 5.5% in patients with a history of thrombosis, 6% if high titer of IgG anticardiolipin
- Includes lupus anticoagulant (most patients do not have SLE), anticardiolipin antibody and anti β2 glycoprotein antibodies
- Antibodies are against phospholipids (usually transient, secondary to infection) or various plasma protein antigenic targets (β2-glycoprotein I, protein C, protein S, annexin V, high and low molecular weight kininogens, thrombomodulin, prothrombin, factors XI and XII, complement factor H)
- First described by Wassermann in 1906 (Wasserman test was complement fixation procedure using saline liver extracts from fetuses with congenital syphilis)
- Associated with an increased risk of arterial or venous thrombosis, thrombocytopenia, recurrent miscarriages; causes 1 / 3 of strokes in patients younger than age 50 years (often due to mitral or aortic valve emboli), 15% of deep venous thromboses, 5 - 15% of recurrent spontaneous abortions, eclampsia, maternal DVT's; also multi infarct dementia, chorea, migraine, livedo reticularis in skin
- Catastrophic antiphospholipid syndrome resembles TTP-HUS
- Antiphospholipid antibody syndrome: diagnosis requires a positive lupus anticoagulant or anticardiolipin antibody on 2 separate occasions, at least 6 - 12 weeks apart and either venous or arterial thrombosis, thrombocytopenia or recurrent fetal loss
- References: Arch Pathol Lab Med 2002;126:1424, J Thromb Haemost 2006;4:295
