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lupus anticoagulant

Etiology: 1) lupus erythematosus (30%) & other autoimmune disorders 2) infections a) bacterial infection b) viral infection, especially HIV c) protozoal infection 3) pharmacologic agents a) chlorpromazine (Thorazine) b) procainamide c) hydralazine d) antibiotics e) cocaine f) Dilantin g) quinidine h) quinine 4) lymphoproliferative disorders a) Waldenstrom's macroglobulinemia b) lymphoma c) hairy cell leukemia Epidemiology: found in 2% of normal individuals Pathology: 1) antiphospholipid antibody - antibodies to cardiolipin may be present 2) prolonged PTT (in vitro phenomenon) 3) confers hypercoagulable state in vivo a) predisposes to arterial & venous thrombosis b) possible mechanisms 1] interference with anticoagulant activity of protein C 2] activation of platelets 3] inhibition of PGI2 production by endothelial cells Laboratory: 1) lupus anticoagulant may be suspected when a prolonged PTT is not correcting by mixing the patient's plasma 50:50 with control plasma (indicating an inhibitor of in vitro anticoagulation) 2) lupus anticoagulant in plasma is confirmed by: a) comparing the PTT of the patient's plasma to control plasma in the presence of a dilute solution of phospholipids b) dilute Russell's viper venom clotting time 3) abnormal aPTT is corrected by substituting activated or resting platelets for exogenous phospholipid 4) hexagonal phospholipid neutralization test is useful when the patient is anticoagulated with heparin or warfarin Management: see antiphospholipid syndrome

Related

anticoagulant antiphospholipid syndrome (APS); Hughes syndrome hexagonal phospholipid neutralization test

General

autoantibody

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 384, 396
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
  3. Clinical Diagnosis & Management by Laboratory Methods, 19th edition, J.B. Henry (ed), W.B. Saunders Co., Philadelphia, PA. 1996, pg 738
  4. Panel of 12 tests Laboratory Test Directory ARUP: 30181
  5. Panel of 16 tests Laboratory Test Directory ARUP: 30268
  6. Panel of 16 tests Laboratory Test Directory ARUP: 2003222