ABSTRACT
Patients with antiphospholipid antibody syndrome (APS) experience a higher rate of recurrence of thrombosis than the general population of patients with thrombotic disease. Based on a retrospective analysis, it has been suggested that patients with APS should be kept on prolonged anticoagulation aiming at international normalised ratio (INR) values > 3.0. To evaluate whether the requirement for more intense anticoagulation depends on the variable sensitivity of thromboplastin reagents to the influence of aPLA, we monitored oral anticoagulant treatment in 10 patients with persistent lupus anticoagulants (LA) and venous thromboembolic disease using two thromboplastin reagents: Pro-IL-Complex (Instrumentation Laboratory, combined) and Recombiplastin (Ortho, recombinant). Acenocoumarol dosage was always assigned based on INR values obtained with the combined thromboplastin using diluted (1:20) test plasma, aiming at an INR interval of 2.0 to 3.0. Single INR determinations with both reagents were obtained throughout the study period for 110 aPLA-free patients on stable oral anticoagulation. Using the manufacturer's instrument-certified international sensitivity index (ISI) values, INR obtained with the recombinant reagent were significantly higher than those obtained with the combined reagent in LA-positive patients, but they were lower in LA-negative patients. After correction for local ISI calibration in LA-negative patients, INR values of 3.1 and 4.6 with Recombiplastin corresponded, respectively, to INR values of 2.0 and 3.0 with Pro-IL-Complex. These results indicate the thromboplastin-dependency of INR values in patients with LA, thereby questioning the validity of the INR system for the monitoring of oral anticoagulant treatment in these patients.
Subject(s)
Anticoagulants/administration & dosage , Antiphospholipid Syndrome/drug therapy , Lupus Coagulation Inhibitor/analysis , Partial Thromboplastin Time , Thromboembolism/drug therapy , Administration, Oral , Antiphospholipid Syndrome/complications , Antiphospholipid Syndrome/immunology , Female , Humans , Indicators and Reagents , Male , Reproducibility of Results , Retrospective Studies , Sensitivity and Specificity , Thromboembolism/etiologyABSTRACT
Two young adults with lupus anticoagulant had multiple attacks of cerebrovascular ischemia in different arterial territories. Cerebral angiography was normal. One patient had a new episode during anticoagulant therapy, but has remained asymptomatic on antiplatelet treatment. In the other, further events occurred during treatment with platelet-inhibiting drugs, but there have been no recurrences with adequate anticoagulant therapy. Lupus anticoagulants are possible causes of otherwise unexplained thromboembolic events. Due to the variable mode of action of these immunoglobulins, platelet-inhibiting drugs may in some cases be considered as a prophylactic alternative to anticoagulant treatment.
