Diagnostic performance of time-resolved fluoroimmunoassay based anti-phospholipase A2 receptor antibody detection for primary membranous nephropathy

Detection of anti-phospholipase A2 receptor (PLA2R) antibody levels is a non-invasive method for the diagnosis of primary membranous nephropathy (PMN). However, diagnosing PMN becomes challenging when anti-PLA2R antibody levels are less than 20 RU/ml. Therefore, this investigation aimed to assess the diagnostic efficacy of time-resolved fluorescence immunoassay (TRFIA) for the detection of anti-PLA2R antibodies. A total of 201 patients with anti-PLA2R antibody levels between 2 and 20 RU/ml were included. Baseline serum samples were tested via ELISA and both direct and indirect TRFIA. Renal biopsy results indicated that 56% patients were diagnosed as PMN. The direct and indirect TRFIA demonstrated significant improvement in sensitivity and specificity for the detection of anti-PLA2R-IgG/IgG4. Indirect TRFIA showed the best sensitivity and specificity for the detection of anti-PLA2R-IgG4, with an optimal cutoff value of 65.34 ng/ml (sensitivity/specificity: 83.9%/94.4%). Logistic regression analysis indicated that anti-PLA2R-IgG4 detected via indirect TRFIA serves as an independent diagnostic marker for PMN patients with low antibody titers (OR = 62.097, P < 0.001). In conclusion, both direct and indirect TRFIA exhibit significant advantages in the diagnosis of PMN, particularly with anti-PLA2R-IgG4 detected by indirect TRFIA. These methods facilitate more accurate diagnosis of PMN and reduce reliance on invasive renal biopsies.