Evaluation of the usefulness of the mixing test performed in our hospital: Comparison of the waveform pattern method and the index of circulating anticoagulant

Abstract

The prolongation of clotting time such as prothrombin time (PT) and activated partial thromboplastin time (APTT) can be caused by coagulation factor deficiency, coagulation factor inhibitor and antiphospholipid antibody such as lupus anticoagulant (LA). The mixing test is performed to rapidly differentiate these causes of the prolongation of clotting time. We evaluated the usefulness of the mixing test performed in our hospital. The mixing test results were judged using the visual waveform pattern method and the index of circulating anticoagulant (ICA). In all three coagulation-factor-deficient cases, both judgment methods showed a coagulation-factor-deficient pattern. On the other hand, in four out of six LA cases, both judgment methods showed an inhibitor pattern. However, in one LA case (case 8), only ICA showed an inhibitor pattern. Moreover, in another LA case (case 9), both judgment methods showed a coagulation-factor-deficient pattern. The LA activities in cases 8 and 9 tended to be lower than those in the four cases that showed an inhibitor pattern in both judgment methods. In this study, we were able to estimate the causes of the prolongation of clotting time in eight out of nine cases. The mixing test was useful for rapidly differentiating the causes of the prolongation of clotting time. However, the cases with the low LA activity may show a coagulation-factor-deficient pattern in the judgment of the mixing test results, so it seems preferable to conduct an additional test if necessary.