Background: The objective of this study was to develop a highly sensitive time-resolved fluorescence immunoassay (TRFIA) method to detect phospholipase A2 receptor (PLA2R)-IgG1 antibodies and evaluate its clinical relevance in predicting the prognosis of individuals with idiopathic membranous nephropathy (IMN).

Methods: A three-step indirect TRFIA method was established using a PLA2R antigen-coated microtiter plate to capture PLA2R-IgG antibodies, followed by detection using mouse anti-human IgG1 and Eu3+-labeled goat anti-mouse IgG antibodies. This method was applied to the initial serum of 56 patients with PLA2R-IMN to investigate the clinical value of PLA2R-IgG1 antibody levels in predicting IMN prognosis.

Results: The detection range of PLA2R-IgG1-TRFIA was 0.85-300RU/mL, with intra-assay precision of 3.54-5.93 % and inter-assay precision of 4.39-9.36 %. Recoveries were 101.77-108.04 %. A PLA2R-IgG1 level above 2.21RU/mL indicated PLA2R-IMN. At initial diagnosis, the median PLA2R-IgG level was 51.24RU/mL in the remission group and 93.27RU/mL in the non-remission group. The median PLA2R-IgG1 level was 603.32RU/mL in the non-remission group, which was 4.29 times higher than that in the remission group (140.67RU/mL). PLA2R-IgG1 levels (P = 0.001) more effectively distinguished between remission and non-remission groups compared with PLA2R-IgG levels (P = 0.094).

Conclusions: The first quantitative TRFIA for PLA2R-IgG1 was established, showing greater clinical value in predicting IMN prognosis, compared to that for PLA2R-IgG levels.