Supplementary Material for: Response Predictors to Calcineurin Inhibitors in Patients with Primary Membranous Nephropathy

Background: Currently, there is an urgent need to find ways of identifying primary membranous nephropathy (PMN) patients who are likely to benefit from calcineurin inhibitors (CNI) or who are resistant to them. In this study, we employed nano-HPLC-MS/MS analysis to identify serum biomarkers that predict the clinical response to CNI therapy in PMN patients. Methods: The endpoint was complete remission (CR) after CNI treatment. PMN patients were grouped into no-remission (NR) or CR groups to screen predictive candidates using the nano-HPLC-MS/MS analysis. Results: Compared with NR patients, 3 upregulated proteins and 5 downregulated proteins were found to present a twofold change in CR patients’ serum. Serum amyloid A1 protein (SAA1) was further validated by ELISA; it was decreased in patients in the NR group compared with patients in the CR group, but SAA1 in patients in these groups was lower than in healthy controls and minimal change disease patients. The area under the receiver operating characteristic (ROC) curve of SAA1 was used to distinguish PMN NR patients from those in remission and was 0.901, with a sensitivity of 78.3% and specificity of 86.8%, similar to that of the phospholipase A2 receptor (PLA2R) antibody. Combining SAA1 with the PLA2R antibody, the area under the ROC curve was 0.956, which was higher than that of SAA1 or the PLA2R antibody alone. Conclusions: Serum SAA1 may be a candidate PMN biomarker that can be used to discriminate CNI NR cases from remission patients. The combination of SAA1 and the PLA2R antibody increases the accuracy of diagnosis.