PLA2R and membranous nephropathy: A 3 year prospective Australian study

AIM: The phospholipase A2 receptor (PLA2R) is the major target antigen in idiopathic membranous nephropathy (iMN). The aim of this prospective study was to determine the prevalence of anti-PLA2R in iMN in an Australian cohort. METHODS: Serum anti-PLA2R was measured using two techniques, an enzyme-linked immunosorbent assay (ELISA) and a cell-based indirect immunofluorescence test. Kidney biopsies were also examined for the presence of PLA2R using a polyclonal antibody. A group of 21 patients with iMN were compared with a group of 19 patients with secondary MN and other glomerular diseases. RESULTS: Seventeen of 21 patients with iMN were positive for anti-PLA2R on both ELISA and indirect immunofluorescence test, and 14 of these patients also had positive staining for PLA2R in the biopsy (tissue was unavailable in two patients). Three patients with iMN had positive staining in the biopsy only, and one patient was negative in both the serum and the biopsy. None of the patients with secondary MN or other glomerular diseases had anti-PLA2R antibodies or PLA2R in the biopsy. There was wide inter-individual variation in titre on ELISA, but serial levels within an individual patient enabled monitoring of disease, and a fall in titre correlated with clinical remission. CONCLUSIONS: This is the first Australian series to examine the incidence of anti-PLA2R in iMN. It is also unique in examining sera by two separate techniques in conjunction with tissue localization of PLA2R. We have shown 100% specificity of both serum anti-PLA2R and glomerular PLA2R in iMN, with a sensitivity of 81.0%. When serum testing is combined with tissue localization of PLA2R, the sensitivity increases to 95.2%.