Supplementary Material for: Serum Anti-PLA2R Antibody Predicts Treatment Outcome in Idiopathic Membranous Nephropathy

Background: M-type phospholipase A₂ receptor (PLA₂R) has been identified as the major target antigen in idiopathic membranous nephropathy (IMN). However, the role of glomerular PLA₂R (gPLA₂R) and the associations of serum anti-PLA₂R antibody (sPLA₂R-Ab) titre with diagnosis, treatment and prognosis in IMN need to be further investigated. Methods: We screened 148 consecutive patients with biopsy-proven membranous nephropathy (MN; 113 with IMN and 35 with secondary MN (SMN)) who were followed up for ≤20 months. Serum and urine samples were simultaneously collected at different time points. The levels of sPLA₂R-Ab were detected using immunofluorescence and enzyme-linked immunosorbent assay. gPLA₂R was assessed by immunofluorescence. Results: Most patients with IMN displayed both gPLA₂R and sPLA₂R-Ab positive (85.8 and 82.3%, respectively). In contrast, very few patients with SMN showed either gPLA₂R or sPLA₂R-Ab positive. The sPLA₂R-Ab titre, not gPLA₂R, was significantly correlated with proteinuria. Surprisingly, changes in sPLA₂R-Ab titre occurred earlier and faster than proteinuria in patients who were followed up for ≤20 months during the whole period of observation. Survival analysis of IMN patients indicated a significant association between sPLA₂R-Ab titre and outcome, whereas, no significant difference was observed between the gPLA₂R intensity and outcome. Conclusions: These data indicate that sPLA₂R-Ab might be a better biomarker for IMN diagnosis and treatment outcome. In addition, monitoring sPLA₂R-Ab titre may assist in determining when to initiate the administration of immunosuppressive agents and in evaluating treatment efficacy.