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

Introduction: 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.

Methods: 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.

Results: 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.

Conclusion: 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.