Background Currently, ELISA for detection of anticardiolipin (aCL) and anti-β2Glycoprotein I (anti-β2GPI) antibodies is not standardized. Recently, few studies have compared the performance of ELISA with that of Fluorescence enzyme immunoassay (FEIA), but they have produced debatable results.
Objectives The aim of this investigation was to compare ELISA with FEIA results in detecting aCL and anti-β2GPI antibodies and to evaluate the diagnostic value of FEIA through the analysis of a group of ELISA negative patients with clinical manifestations of APS.
Methods The study cohort included 94 primary antiphospholipid syndrome (PAPS) patients, 65 subjects with the clinical criteria for PAPS classification but ELISA negative for the laboratory criteria and 78 healthy subjects age- and sex-matched to the patients. Serum IgG/IgM aCL/anti-β2GPI antibodies were determined using FEIA-EliA™ and a home-made ELISA. The cut-off values were calculated as > the 99th percentile using sera from 78 healthy controls.
Results The data obtained with the two techniques are showed in the table, in particular, the sensitivities of the two methods were similar with the exception of IgM aCL which were found to be significantly prevalent in the PAPS patients using the ELISA method. The two techniques 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.
Conclusions Our results suggest that FEIA is comparable to a home-made ELISA which is currently the most widely test used for aPL detection. These results could support the routine use of FEIA-EliA™ in detecting aCL and anti-β2GPI antibodies on PAPS patients. However, only its use on a large scale will indicate in the future if it can be considered a valid method for classification of PAPS.
Disclosure of Interest None declared