Comparative analysis of immunoassay methods for the determination of circulating antibodies to the phospholipase A₂ receptor

THE AIM. Comparison of indirect immunofluorescence (IIFT) and enzyme-linked immunosorbent assay (ELISA) methods for the determination of circulating antibodies to the podocytic transmembrane receptor of M-type secreted phospholipase A₂ (PLA₂R-AB) in patients with primary membranous nephropathy (PMN). PATIENTS AND METHODS. The study included 54 patients with PMN (M: F [33:21]) aged 55 (40-63) years and 10 apparently healthy individuals of the corresponding gender and age. Proteinuria and glomerular filtration rate (eGFR) was determined in all patients. The anti-PLA₂R-AB levels were measured by indirect immunofluorescence (IIFT) and enzyme-linked immunosorbent assay (ELISA) using EURUIMMUN AG test systems (Lubeck, Germany). RESULTS. The levels of anti-PLA₂R-АB determined by the two investigated methods were changed in the same direction (r = 0.82, p < 0.005). The ELISA method made it possible to detect a larger number of anti-PLA₂R-positive cases, both in the group of patients before treatment (ELISA – up to 80 %, IIFT – up to 67 %) and among patients receiving immunosuppressive therapy (ELISA – up to 63 %, IIFT – up to 50 %). The concentration of autoantibodies determined by ELISA (both quantitative and semi- quantitative) correlated with proteinuria (r = 0.69, p = 0.001) and eGFR (r = -0.38, p = 0.035). The response to therapy was more clearly traced when the study was performed by quantitative ELISA. CONCLUSION. The ELISA method is more effective in identifying PLA₂R-positive patients with PMN, allows obtaining quantitative results and assessing the dynamics of the concentration of autoantibodies, which contributes to the early correction of the therapy and decisionmaking on immunosuppressive treatment.

membranous nephropathy, treatment, autoantibodies, phospholipase A₂ receptor

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