Lupus anticoagulant in the blood

Reference values (norm) of the lupus anticoagulant in the blood plasma are 0,8-1,2 conv. Units

Lupus anticoagulant refers to the Ig class IgG and is an antibody 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 systemic lupus erythematosus. The presence of lupus anticoagulant in patients can be suspected with unexplained prolongation of APTT, time of recalcification and, to a lesser extent, prothrombin time with normal results of all other coagulogram indices. Lupus anticoagulant is usually detected by lengthening in patients with APTT, while they do not show severe bleeding, and in 30% develops thrombosis, that is, a paradoxical combination is observed - APTT prolongation and propensity to thrombosis. The mechanism of thrombosis development in patients with lupus anticoagulant is not exactly established at present, however it is known that antiphospholipid antibodies reduce prostacyclin production by endothelial cells due to inhibition of phospholipase A ₂ and protein S and, thus, create prerequisites for thrombosis. Currently, lupus anticoagulant 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, antiphospholipid syndrome, in patients with HIV infection (20-50%), in women with habitual miscarriages and intrauterine fetal death, in patients with complications of drug therapy. Approximately 25-30% of patients with lupus anticoagulant develop thromboembolism. In systemic lupus erythematosus, lupus anticoagulant is detected in 34-44% of patients, and in patients receiving long-term phenothiazine - in 32%. In patients with lupus anticoagulant, false-positive results are often noted in the study of syphilis. The frequency of detection of lupus anticoagulant better correlates with the risk of thrombosis than the frequency of detection of anticardiolipin antibodies.

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

• 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 lupus anticoagulant than the usual APTT; 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 lupus anticoagulant, since 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 is a correction trial, which implies a refinement of the genesis of elongation of 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 the time is shortened by adding excess phospholipids to the test plasma, this is evidence of the presence of lupus anticoagulant, if not, specific inhibitors of clotting factors are present in the plasma.

If the first screening test for lupus anticoagulant is negative, this does not yet indicate its absence. Only with negative results of two screening tests can we judge the absence of a lupus anticoagulant in the blood plasma.

When evaluating the results of a lupus anticoagulant assay with a minimum content of phospholipids, it is necessary to focus on the following data: if the result of a lupus anticoagulant test is 1.2-1.5 conv. Units, the lupus anticoagulant is contained in small quantities, and its activity is small; 1,5-2 conv. Units - lupus anticoagulant is found in a moderate amount, and the likelihood of developing thrombosis increases significantly; more than 2,0 cond. Units - Lupus anticoagulant is present in large numbers and the likelihood of thrombosis is very high.

The definition of lupus anticoagulant and anticardiolipin antibodies is shown to all patients with signs of hypercoagulability, even if the APTT is not elongated.

When appointing a study for lupus anticoagulant, it is necessary to cancel the patient's heparin intake for 2 days, oral anticoagulants - 2 weeks before blood collection, since the presence of these drugs in the blood can give false positive results.

[1], [2], [3], [4], [5], [6], [7], [8]