Urine anti-PLA2R antibody is a novel biomarker of idiopathic membranous nephropathy.

Since urine samples more directly reflect kidney alterations and damage than blood samples, we investigated whether urine anti-PLAR antibody (uPLAR-Ab) could be utilized similarly to serum anti-PLAR antibody (sPLAR-Ab) as a noninvasive biomarker of idiopathic membranous nephropathy (IMN). In this study, we performed a qualitative analysis using an indirect immunofluorescence test (IIFT) and measured uPLAR-Ab and sPLAR-Ab concentrations using an enzyme-linked immunosorbent assay (ELISA) in 28 patients with biopsy-proven IMN and 12 patients with secondary membranous nephropathy (SMN). Overall, 64.3% (=18) of patients with IMN had IIFT-positive sPLAR-Ab, 67.9% (=19) of patients with IMN had IIFT-positive uPLAR-Ab, and none of the SMN patients had IIFT-positive sPLAR-Ab or uPLAR-Ab. The titers of the anti-PLAR antibody from the IMN patients in the urine (10.72±22.24 RU/μmol, presented as uPLAR-Ab/urine creatinine) and serum (107.36±140.93 RU/ml) were higher than those from the SMN patients (0.51±0.46 RU/μmol, 0.008±0.029 RU/ml, respectively, <0.05). Statistical analyses indicated that there were positive correlations between uPLAR-Ab and gPLAR, sPLAR-Ab or urinary protein and negative correlations between uPLAR-Ab and serum albumin in patients with IMN. In conclusion, uPLAR-Ab is a novel biomarker of IMN. sPLAR-Ab combined with uPLAR-Ab might be more helpful for diagnosis and activity in PLAR associated MN.