title: Laboratory detection of the antiphospholipid syndrome via calibrated automated thrombography.
abstract: Lupus anticoagulants (LAC) consist of antiphospholipid antibodies, detected via their anticoagulant properties in vitro. Strong LAC relate to thromboembolic events, a hallmark of the antiphospholipid syndrome. We have analyzed whether detection of this syndrome would benefit from thrombin generation measurements. Therefore, calibrated automated thrombography was done in normal plasma (n = 30) and LAC patient plasma (n = 48 non-anticoagulated, n = 12 on oral anticoagulants), diluted 1:1 with a normal plasma pool. The anti-beta2-glycoprotein I monoclonal antibody 23H9, with known LAC properties, delayed the lag time and reduced the peak height during thrombin generation induction in normal plasma dose-dependently (0-150 microg/ml). At variance, LAC patient 1:1 plasma mixtures manifested variable lag time prolongations and/or peak height reductions. Coupling these two most informative thrombin generation parameters in a peak height/lag time ratio, and upon normalization versus the normal plasma pool, this ratio distributed normally and was reduced in the plasma mixtures, for 59/60 known LAC plasmas. The normalized peak height/lag time ratio correlated well with the normalized dilute prothrombin time, diluted Russell's viper venom time and silica clotting time, measured in 1:1 plasma mixtures (correlation coefficients 0.59-0.72). The anticoagulant effects of activated protein C (0-7.5 nM) or 23H9 (0-150 microg/ml), spiked in the 1:1 LAC plasma mixtures were reduced for the majority of patients, compatible with functional competition between patient LAC and activated protein C and LAC and 23H9, respectively. Hence, the normalized thrombin generation-derived peak height/lag time ratio identifies LAC in plasma with high sensitivity in a single assay, irrespective of the patient's treatment with oral anticoagulants.
authors.affiliation: Coagulation Laboratroy, Department of Clinical Chemistry, Microbiology and Immunology, Ghent University Hospital, Ghent, Belgium.
authors.forename: Katrien
authors.initials: K
authors.lastname: Devreese
authors.forename: Kathelijne
authors.initials: K
authors.lastname: Peerlinck
authors.forename: Jef
authors.initials: J
authors.lastname: Arnout
authors.forename: Marc F
authors.initials: MF
authors.lastname: Hoylaerts
mesh_terms: D000284:Administration, Oral; D017152:Antibodies, Antiphospholipid / Q000097:blood*; D000911:Antibodies, Monoclonal; D000925:Anticoagulants / Q000008:administration & dosage; D016736:Antiphospholipid Syndrome / Q000097:blood / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology; D001331:Automation; D001530:Belgium; D001777:Blood Coagulation; D001780:Blood Coagulation Tests / Q000592:standards*; D002138:Calibration; D016022:Case-Control Studies; D019411:Clinical Laboratory Techniques / Q000592:standards*; D006801:Humans; D007700:Kinetics; D011237:Predictive Value of Tests; D011486:Protein C / Q000378:metabolism; D011517:Prothrombin Time / Q000592:standards; D012680:Sensitivity and Specificity; D013917:Thrombin / Q000378:metabolism*; D053482:beta 2-Glycoprotein I / Q000097:blood
chemical_list: D017152:Antibodies, Antiphospholipid; D000911:Antibodies, Monoclonal; D000925:Anticoagulants; D011486:Protein C; D053482:beta 2-Glycoprotein I; D013917:Thrombin