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

<strong><em>Background:</em></strong> M-type phospholipase A<sub>2</sub> receptor (PLA<sub>2</sub>R) has been identified as the major target antigen in idiopathic membranous nephropathy (IMN). However, the role of glomerular PLA<sub>2</sub>R (gPLA<sub>2</sub>R) and the associations of serum anti-PLA<sub>2</sub>R antibody (sPLA<sub>2</sub>R-Ab) titre with diagnosis, treatment and prognosis in IMN need to be further investigated. <b><i>Methods:</i></b> 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 sPLA<sub>2</sub>R-Ab were detected using immunofluorescence and enzyme-linked immunosorbent assay. gPLA<sub>2</sub>R was assessed by immunofluorescence. <b><i>Results:</i></b> Most patients with IMN displayed both gPLA<sub>2</sub>R and sPLA<sub>2</sub>R-Ab positive (85.8 and 82.3%, respectively). In contrast, very few patients with SMN showed either gPLA<sub>2</sub>R or sPLA<sub>2</sub>R-Ab positive. The sPLA<sub>2</sub>R-Ab titre, not gPLA<sub>2</sub>R, was significantly correlated with proteinuria. Surprisingly, changes in sPLA<sub>2</sub>R-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 sPLA<sub>2</sub>R-Ab titre and outcome, whereas, no significant difference was observed between the gPLA<sub>2</sub>R intensity and outcome. <b><i>Conclusions:</i></b> These data indicate that sPLA<sub>2</sub>R-Ab might be a better biomarker for IMN diagnosis and treatment outcome. In addition, monitoring sPLA<sub>2</sub>R-Ab titre may assist in determining when to initiate the administration of immunosuppressive agents and in evaluating treatment efficacy.<br>