Evaluation of mixing tests and the index of circulating anticoagulant in detecting lupus anticoagulants

Abstract

Introduction: For the diagnosis of lupus anticoagulants (LAC), the mixing tests (MT) and the index of circulating anticoagulant (ICA) are considered useful to differentiate factor deficiency from inhibitor. However, the clinical usefulness of the percentage of correction of MT (%C-MT) and ICA still needs to be investigated. Objectives: To evaluate the clinical usefulness of %C-TM and ICA of diluted Russells viper venom (dRVVT) and silica clotting time (SCT) screening tests in identifying LAC, as well as to verify their responses to warfarin, enoxaparin, and direct oral anticoagulants (DOACs). Methods: Analysis of 605 patient samples tested for dRVVT and SCT (103 positives for LAC and 502 negatives), 28 using warfarin, 14 using enoxaparin, and 22 using DOACs. Results: The parameters showed the following values of sensitivity, specificity, positive predictive value, negative predictive value, and efficiency, respectively, in the diagnosis of LAC: %C-dRVVT-SCREEN-MIX (83.1%; 65.6%; 77%; 73.6%; 79.5%); ICA-dRVVT-SCREEN-MIX (75%; 89.9%; 84.2%; 83.3%; 86.6%); %C-dRVVT-CONFIRM (76.4%; 94.3%; 95%; 72%; 90.3%); %C-SCT-SCREEN-MIX (45.9%; 86.9%; 82.6%; 54.1%; 69.4%); ICA-SCT SCREEN-MIX (78.8%; 90.4%; 85.7%; 85.3%; 90.9%), and %C-SCT-CONFIRM (82.5%; 92.6%; 95%; 75%; 93.9%). The ICA and %C-MT of LAC-positive samples were in most cases significantly higher and lower, respectively, compared to normal, warfarin, enoxaparin, and DOACs. Conclusion: The ICA and %C-MT of dRVVT and SCT can be considered useful and reliable tools in the interpretation of dRVVT and SCT tests in the identification of LAC.