negative results of the all examined patients. However, due to low Se it's impossible to narrow the quantity of patients with the APS possibility. On the mix-stage we observed the low Se and high Sp of index of circulating anticoagulant (ICA) all the tests (c 2 >44,74; P < 0,001). On the confirmatory stage Se for LA ratio of all the test was 61,5% -74,4% and Sp LA ratio -95,4% -98,4% (c 2 >87,42; P < 0,001). Ac of all the tests was >87,8% Summary/Conclusion: Coagulation tests of the first stage have a high diagnostic reliability due to considerable Sp and Ac. Low Se does not give a considerable certainty of anticoagulant absence if the coagulation time is within the norm. On the second stage with ICA >15,0% LA can be suspected with high probability, but the low Se does not allow us to confidently differentiate the deficiency of clotting factor from the presence of pathological inhibitors. The highest significant diagnostic efficacy was found in the confirmatory stage.