The cutoff value and prognosis of anti-PLA2R antibody for idiopathic membranous nephropathy: a single-center retrospective study in China

Serum anti-phospholipase A2 receptor (anti-PLA2R) antibody is used for the noninvasive diagnosis of idiopathic membranous nephropathy (IMN). However, the cutoff value of anti-PLA2R antibodies in IMN patients is debatable. This study aimed to investigate the cutoff value of anti-PLA2R antibodies for diagnosing IMN and the correlation of anti-PLA2R antibodies with clinical parameters and prognosis. A total of 252 IMN patients and 521 non-IMN patients with both renal biopsy and serum anti-PLA2R antibody data from April 2017 to November 2019 were enrolled. Anti-PLA2R antibody was detected by an enzyme-linked immunosorbent assay. The anti-PLA2R antibody titer was higher in the IMN group than in the non-IMN group (153.1 ± 22.4 vs. 2.0 ± 0.2 RU/mL, p < 0.001). The optimal anti-PLA2R antibody cutoff value for diagnosing IMN was 2.5 RU/mL, with a sensitivity, specificity, and Youden index of 85.7%, 88.3%, and 0.740, respectively. There was a significant positive correlation between anti-PLA2R antibody and 24-h urinary protein levels (r = 0.341, p < 0.001), and a significant negative correlation between anti-PLA2R antibody and serum albumin levels (r=−0.274, p < 0.001) in patients with IMN. The remission rates positively correlated with the immunosuppressive usage rates and increased from the low- to the high-titer subgroup. Multivariable Cox regression analysis showed that immunosuppressive therapy (adjusted HR = 4.656; 95% confidence interval [CI], 1.461–14.839; p = 0.009) was associated with a higher remission rate in patients with IMN. The optimal Anti-PLA2R antibody cutoff value for diagnosing IMN was 2.5 RU/mL, which was much lower than that indicated by the manufacturer. If IMN is actively treated, patients can have much better prognoses. Trial registration: retrospectively registered.