Hui Li, Ya Zhang, Xiaomin Ding, Chong Zhang
Objectives The protein selectivity index (PSI) has been proposed as a prognostic marker in nephrotic syndrome, but its prognostic value in primary membranous nephropathy (PMN) has not been well established in the modern era of advanced diagnostics and therapeutics. This study assessed the predictive value of PSI for proteinuria remission and response to rituximab therapy.Methods A total of 73 patients with PMN treated between September 2021 and September 2024 were included in this single-center retrospective study, all with at least six months of follow-up. PSI was calculated from serum and urinary immunoglobulin G and transferrin.Results The optimal PSI cutoff for predicting complete remission was 0.303. Low-PSI (<0.303) patients had higher complete remission rates than high-PSI (≥0.303) patients (59.65% vs. 12.50%, p = 0.001). No significant differences were observed in eGFR changes or CKD progression. Kaplan-Meier analysis demonstrated a significantly higher cumulative incidence of complete remission in the low-PSI group (p = 0.016). Cox regression confirmed that patients with low PSI were more likely to achieve complete remission (HR = 4.88, 95% CI: 1.17–20.36, p = 0.030). In the rituximab subgroup, a cutoff of 0.313 identified better responders (51.35% vs. 0%, p = 0.003). The albumin-based alternative index correlated strongly with traditional PSI (r = 0.839, p < 0.001).Conclusions In conclusion, PSI predicts proteinuria remission and treatment response in PMN. Prospective multicenter studies are needed to validate its clinical utility.