PB2423 THE DIAGNOSTIC RELIABILITY OF TESTS DETECTION OF LUPUS ANTICOAGULANT

Background: Antiphospholipid syndrome (APS) is an acquired autoimmune disorder that manifests clinically as recurrent venous or arterial thrombosis and/or fetal loss. Characteristic laboratory abnormalities in APS include persistently elevated levels of antiphospholipid antibodies (lupus anticoagulant (LA), anticardiolipin antibody, and/or anti‐beta2‐glycoprotein I) Aims: Finding the most informative coagulologic tests for the detection of LA in patients with suspected APS by identifying diagnostic laboratory eligibility criteria (sensitivity, specificity, accuracy and likelihood ratio) for each of these tests Methods: In 233 patients with suspected APS the presence of lupus anticoagulant (LA) was examined on the basis of a three‐step test carried out in accordance with the current guidelines. We used clotting time with diluted viper venom time (DVVT), activated partial thromboplastin time (APTT) with LA ‐sensitive reagent and prothrombin time (PT) with diluted to 50 and 500 times thromboplastin. We calculated sensitivity (Se), specificity (Sp) and accuracy (Ac) for each of these tests Results: APS was diagnosed in 44,6% of patients. LA was identified in 42,5% of all the patients, which is 95,2% of all patients with APS. On the first stage a considerable Sp >75,0% (χ2 > 60,0; p < 0,001) of all phospholipid ‐ dependent coagulation test. Ac of the first stage tests does not go <75,0% which indicates a fairly big part of true positive and true 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 (χ 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% (χ 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.