To analyze the antibody level of phospholipase A2 receptor (PLA2R) in Chinese patients with primary membrane nephropathy (PMN) and its correlation with clinical indicators, and to explore more suitable cut-off value for Chinese patients.

All hospitalized patients with renal biopsy at Peking University People's Hospital from January to August 2018 were retrospectively reviewed. According to the primary disease, patients were divided into PMN group (including patients with idiopathic membranous nephropathy and atypical membranous nephropathy of unknown cause) and control group (other pathological types, including secondary membranous nephropathy patients). Their clinical and pathological characteristics were analyzed, and the level of serum PLA2R antibodies was detected using the method of enzyme-linked immunosorbent assay (ELISA). Spearman correlation was used to analyze the correlation between PMN patients' blood anti-PLA2R antibody level and clinical indicators. The risk factors of PMN were analyzed by logistic regression model, and the optimal cut-off value of PMN was analyzed by ROC curve.

A total of 354 patients were included in this study, including 114 patients in PMN group and 240 patients in control group. The age of PMN group was (51.7±14.1) years old and the ratio of male to female was 2.2∶1. The median concentration of PLA2R antibody in PMN group was 16.87 RU/ml [inter-quartile range (IQR) 1.88-57.26], which was significantly higher than that in control group (1.43 RU/ml, IQR 1.20-1.62, P<0.001). In PMN group, the concentration of anti-PLA2R antibody was correlated with the 24-hour urine protein ration (r=0.278, P=0.003) and urine erythrocyte (r=0.190, P=0.043), but not with serum albumin (r=-0.149, P=0.114) and serum creatinine (r=0.136, P=0.149). The ROC curve showed that the sensitivity of distinguishing PMN from other diseases was 69.3% (95%CI 60.3%-77.0%), the specificity was 92.9%(95%CI 89.0%-95.5%), and the area under the curve was 0.859(95%CI 0.813-0.905) when the cut-off value was set as 2.28 RU/ml, which was significantly better than the cut-off value of 20.00 RU/ml (the sensitivity/specificity was 46.5%/97.5%) and 14.00 RU/ml (the sensitivity/specificity was 53.5%/97.1%).

PLA2R antibody is one of the main pathogenic antibodies of PMN. In China, it is recommended to lower its cut-off value to 2.28 RU/ml, which can improve the sensitivity of distinguishing PMN from other pathological types without reducing specificity.

Glomerulonephritis, membranous; Receptor, phospholipa A2; Diagnosis, differential; Cut-off value; Anti-phospholipase A2 receptor antibody