Optimal Value for Serum Anti-PLA2R Antibody in Primary Membranous Nephropathy: A Multicenter Observational Study

Anti-phospholipase A2 receptor antibody (PLA2R-Ab) is highly specific for primary membranous nephropathy (PMN). Here, we compare the diagnostic value of different circulating PLA2R-Ab cutoff titers in multicenter cohorts, with particular focus on determining the optimal cutoff value for Chinese patients.In total, 288 patients with PMN and 301 with other nephropathies were recruited retrospectively from five hospitals in China between September 2011 and October 2018. PLA2R-Ab in serum obtained at renal biopsy was determined by enzyme-linked immunosorbent assay. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and receiver operating characteristic (ROC) curve of PLA2R-Ab in diagnosing PMN were assessed. Diagnostic efficiency was evaluated by internal validation.The sensitivity, specificity, PPV, NPV, and Youden index for PMN diagnosis were 71%, 90%, 88%, 75%, and 0.61 at the cutoff of 3.8 RU/mL; 74%, 86%, 84%, 76%, and 0.60 at 2.7 RU/mL; 68%, 92%, 90%, 73%, and 0.60 at 5.2 RU/mL; 64%, 95%, 93%, 72%, and 0.59 at 9.0 RU/mL; 57%, 96%, 94%, 68%, and 0.54 at 14.0 RU/mL; 51%, 97%, 95%, 66%, and 0.49 at 20.0 RU/mL; 47%, 98%, 96%, 64%, and 0.45 at 40.0 RU/mL, respectively. The area under the ROC curve was 0.83.By comprehensively considering specificity and sensitivity, we show that 3.8 RU/mL is the optimal cutoff of PLA2R-Ab in Chinese PMN patients, with a sensitivity of 71% and a specificity of 90%. The cutoff values were 5.2 RU/mL and 9.0 RU/mL when the diagnostic specificity was increased to 92% and 95%, respectively.