Immunoassay Detects Specific Antibodies in Antiphospholipid Syndrome Patients

Currently, enzyme-linked immunosorbent assays (ELISA) for detection of anticardiolipin (aCL) and anti-β2glycoprotein I (anti-β2GPI) antibodies has not been standardized.

Antiphospholipid (aPL) antibodies are a heterogeneous group of autoantibodies directed against plasma protein-phospholipid complexes or single plasma proteins and their presence in patients with thrombosis and/or pregnancy morbidity defines antiphospholipid syndrome.


Scientists at the University of Padova (Italy) collected blood samples from 94 primary antiphospholipid syndrome (PAPS) patients (84 females and 10 males, mean age 44.3 ± 11.7 years, range 20 to 79) who fulfilled the classification criteria for definite antiphospholipid syndrome. Forty-three had a history of thrombosis, 38 of pregnancy morbidity, and 13 of both thrombosis and pregnancy morbidity.

Serum immunoglobulin G/M (IgG/IgM) aCL/anti-β2GPI antibodies were determined using a fluorescence enzyme immunoassay (FEIA-EliA, Phadia AB; Uppsala, Sweden) and an in-house ELISA. The fluorescence in the reaction mixture was measured using the Phadia 250 instrument. Higher fluorescent signal values corresponded to larger quantities of antibodies binding to the antigens. IgG/IgM aCL and IgG/IgM anti-β2GPI ELISA assays were performed using a home-made method following the European Forum on antiphospholipid (aPL) recommendations.

The sensitivities of the two methods were similar with the exception of IgM aCL which was found to be significantly higher in the PAPS patients using the ELISA method, even if IgM aCL was detected at a low level by both techniques. The two assays had a comparable specificity, a high/significant agreement and a significant correlation between the antibody levels. FEIA testing uncovered no significant prevalence of any antiphospholipid (aPL) antibody in the ELISA negative patients.

The authors concluded that FEIA, like other fully automated systems, may be considered as a useful assay for laboratories with a large number of samples and moreover, it reduces operator handling, pipetting errors and differences in protocols. The results of the study support FEIA's routine use in detecting aCL and anti-β2GPI antibodies. The study was published in the June 2015 issue of the journal Clinica Chimica Acta.

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