The Sensitivity and Specificity of Serum Phospholipase A2 Receptor Antibodies in Diagnosing Primary Membranous Nephropathy in Patients with Adult Nephrotic Syndrome and its Correlation with Serum Phospholipase A2 Receptor Staining in Kidney Biopsies

Abstract

Membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome (NS) in nondiabetic adults, with about 70%–80% of cases of MN being primary MN (pMN). Many studies have shown that serum phospholipase A2 receptor (PLA2R) antibodies are a diagnostic and prognostic biomarker for pMN, with a pooled diagnostic sensitivity and specificity of 54%–82% and 89%–100%, respectively, resulting in PLA2R staining and serum PLA2R antibodies being incorporated in the management algorithms of MN. We studied the sensitivity and specificity of serum PLA2R antibodies for diagnosing pMN and its correlation with PLA2R staining in kidney biopsies in a prospective observational study of 58 adult NS subjects undergoing a kidney biopsy. Serum PLA2R antibodies were determined by indirect immunofluorescence (IF) before the biopsy. Kidney biopsies were sent for light microscopy and IF examinations. Biopsy samples with MN histology were stained for PLA2R antigens. Out of the 58 adult NS subjects, 28 were diagnosed with pMN and one with secondary MN. Serum PLA2R antibodies were positive in 12 subjects with pMN, and one had focal segmental glomerulosclerosis not otherwise specified, giving a sensitivity of 42.8% and specificity of 96.7% for diagnosing pMN. There was a significant association between glomerular staining for PLA2R (24 of 28 subjects) and a diagnosis of pMN by kidney biopsy, with a sensitivity of 82.8%. Cohen's kappa agreement between glomerular staining for PLA2R and a diagnosis of MN was 0.83 (0.57–1.08).