Clinical usefulness of anti-M-type phospholipase-A-receptor antibodies in patients with membranous nephropathy and the comparison of three quantification methods.

Associations between anti-M-type phospholipase A2 receptor (PLA2R) antibodies and disease activity and prognosis have been suggested in primary membranous nephropathy (MN); however, more evidence is needed. We aimed to establish a clinically useful method to measure anti-PLA2R antibodies. We developed a western blot assay and a cell-based enzyme-linked immunosorbent assay (ELISA). Anti-PLA2R antibodies were evaluated retrospectively using these assays and the commercial solid-phase ELISA. Anti-PLA2R antibodies were detected in 12, 6, and 12 out of 23 Japanese patients with biopsy-proven primary MN using the western blot, the cell-based ELISA, and the solid-phase ELISA, respectively. The samples of the lupus MN patients tested negative. The levels of proteinuria correlated moderately with the titres of anti-PLA2R antibodies measured by the three methods (r = 0.39-0.47). Anti-PLA2R antibodies were significantly associated with physicians' decisions on immunosuppressive treatment without prior knowledge of anti-PLA2R antibody positivity (p < .01). In the longitudinal analysis, the titres of anti-PLA2R antibodies measured by the solid-phase ELISA declined significantly following treatment (p = .03). In conclusion, these results suggest the usefulness of anti-PLA2R antibody as a diagnostic, prognostic, and surrogate biomarker in primary MN. The three methods proved to be reliable for measuring anti-PLA2R antibody titres, but their performances differ.