Lupus anticoagulant in blood plasma

Reference values ​​of VA in blood plasma - 0,8-1,2 usl.units

BA refers to Ig IgG class and is AT against negatively charged phospholipids. He received his name due to the fact that it affects phospholipid-dependent coagulation tests and was first detected in patients with SLE.The presence of IA in patients can be suspected with unexplained prolongation of APTT, recalcification time and, to a lesser extent, prothrombin time with normal results of all other coagulogram parameters. VA is usually detected by elongation in patients with APTT, while they have no severe

manifestations of hemorrhage, and 30% develop thrombosis, that is, a paradoxical combination is observed - APTT prolongation and propensity to thrombosis. The mechanism of thrombosis development in patients with VA is not precisely established at present, however it is known that antiphospholipid antibiotics reduce production of prostacyclin by endothelial cells due to inhibition of phospholipase A2 and protein S and, thus, create prerequisites for thrombosis. At present, BA is considered as a significant risk factor in patients with unexplained thrombosis and is often found in various forms of pathology, especially in systemic, autoimmune diseases, APS, in patients with HIV infection( 20-50%), in women with habitual miscarriages and intrauterinefetal death, in patients with complications of drug therapy. Approximately 25-30% of patients with VA develop thromboembolism. In SLE, 34-44% of patients are diagnosed with VA, and in 32% of patients receiving long-term phenothiazine. In patients with IA in the blood, false-positive results are often noted when testing for syphilis. The incidence of VA is better correlated with the risk of thrombosis than the incidence of anticardiolipin AT.

Detection of BA is based on lengthening of phospholipid-dependent coagulation reactions. However, due to the lack of standardization of these studies and ambiguous results in 1990, the Subcommittee on IA of the International Society for Thrombosis and Hemostasis recommended the basic principles of detection of IA.

■ Stage I includes screening studies based on lengthening of phospholipid-dependent coagulation tests. For this purpose, tests such as APTT with a minimum content of phospholipids are used, which is much more sensitive to the presence of BA than the usual APTTV;prothrombin time with diluted tissue thromboplastin;the time of Russell's viper poison;kaolin time. Based on the lengthening of the screening tests, it is impossible to judge the presence of BA because it can be the result of circulation of other anticoagulants, such as specific inhibitors of coagulation factors, PDF, paraproteins, as well as deficiency of clotting factors or presence of heparin or warfarin in plasma.

■ Stage II - correction trial, which implies a refinement of the genesis of lengthening screening tests. To this end, the plasma under investigation is mixed with normal. The shortening of the clotting time indicates a shortage of clotting factors. If time is not corrected, and in some cases even prolonged, this indicates the inhibitory nature of the lengthening of screening tests.

■ Stage III - confirmatory test, the purpose of which is to clarify the nature of the inhibitor( specific or nonspecific).If time is shortened when adding excess phospho-lipids to the test plasma, this is evidence of the presence of VA, if not, plasma inhibitors contain specific inhibitors of clotting factors.

If the first screening test for VA is negative, this does not indicate that it is absent. Only with negative results of two screening tests, one can judge the absence of BA in the blood plasma.

When evaluating the results of the VA trial for APTT with a minimum content of phospholipids, the following data should be oriented: if the result of the VA test is 1.2-1.5 conv.units, VA is contained in small quantities, and its activity is small;1,5-2 conv.units- VA is found in a moderate amount, and the likelihood of developing thrombosis increases significantly;more than 2,0 cond.units- VA is present in large numbers and the likelihood of thrombosis is very high.

The definition of VA and anticardiolipin AT is shown to all patients with signs of hypercoagulability, even if they are not elongated by APTT.