Ranging of Antiphospolipid Antibodies in the Patients With Thrombophilia and Recurrent Miscarriage

Abstract

Laboratory diagnosis of antiphospholipid syndrome (APS) is based on detection of antiphospholipid antibodies (aPLs). E.g., aPLs are directed against conformational epitopes of the so-called “co-factor” proteins: β2-gycoprotein 1 (β2-GP1), annexin V (An V) and prothrombin (Pt) that are formed during interaction with phospholipids – cardiolipin (CL), phosphatic acid (Pha), phosphatidylcholine (Pch), phosphatidylethanolamine (Pe), phosphatidylglycerol (Pg), phosphatidylinositol (Pi), phosphatidylserine (Ps). A routine methodology of detection based on ELISA testing is challenged by new tests when the antigen is absorbed on another kind of support like microbeads or membranes that can influence density of conformational epitopes for aPL’s binding. The aim of our study was to compare the results of aPLs detection by ELISA and multi-line immunodot assay (MLD). We collected blood serum samples from 45 patients with noncardioembolic ischemic strokes, 19 patients with recurrent deep vein thrombosis of lower limbs, 44 females with recurrent miscarriages, and 50 clinically healthy donors. To compare the results of aPL detection by ELISA and MLD kits, the test systems from different manufacturers were evaluated. We used an ELISA kits for detection of antibodies to CL IgG, aCL IgM, β2-GP1 produced by Euroimmun AG (Mr1) and Orgentec Diagnostica GmbH (Mr2) and MLD – for detection of antibodies to CL, β2-GP1, Pch, Pe, Pg, Pi, Ps, AnV and Pt (Medipan GmbH, Mr3). When a cut-off titer was used as the main index, 30.5% of patients were aPLs-positive with ELISA method by Mr1 and 38%, wiht Mr2. By MLD aPls were detected in 30% of patients. In the same cohort, medium and high aPLs titers (> 40 U/mL) were determined in 12% of patients using ELISA kits. Positive and highly positive aPLs titers were determined in 16% when using a new method by Mr3. Medium and high titer were detected only for antibodies to β2-GP1, CL, An V, Pha and Phs. The use of ELISA approach for detection of aPLs in patients with thrombosis and obstetric pathology is associated with relatively high number of low-positive ELISA results. Due to higher sensitivity for medium and high aPLs titers, MLD testing may be used as a confirming method for APS diagnosis.