ObjectiveLaboratory extensively applied enzyme-linked immunosorbent assay (ELISA) to measure anti-phospholipase A2 receptor antibodies (PLA2R-abs) since its diagnostic significance on PLA2R related primary membranous nephropathy (PLA2R-related pMN) was discovered. However, PLA2R-abs determined by ELISA (PLA2R-ELISA) could infrequently yield inconclusive results, specifically a grey-zone defined as PLA2R-abs ranging from 2 to 20 RU/mL. Recently, researchers suggested that double-check grey-zone PLA2R-abs by indirect immunofluorescence (IIF) could improve diagnostic accuracy. We evaluated the diagnostic performance of PLA2R-IIF in assessing PLA2R-related pMN and summarized clinicopathological characteristics of grey-zone population to provide more evidence for clinical practice. MethodsData on demographics, serology and pathology of patients with PLA2R-ELISA grey-zone results and a native kidney biopsy at Peking Union Medical College Hospital from September 2020 to April 2023 were reviewed. Grey-zone samples were analyzed using PLA2R-IIF. Negative results were defined as no fluorescence and positive results were graded according to fluorescence intensity. ResultsThis study included a total of 52 grey-zone patients divided into pMN group (n = 36, 69 %) and non-pMN group (n = 16, 31 %) according to renal pathology reports. pMN patients had higher PLA2R-abs and lower serum creatinine compared to the non-pMN patients (P = 0.003, P < 0.001). No statistically significant differences were observed in 24-hour urine protein and albumin between the two groups. Multiple pathological types were identified in the non-pMN group. The sensitivity and specificity of PLA2R-IIF in PLA2R-ELISA grey-zone population were 72 % and 88 %, respectively, with a total consistent rate of 77 % and a positive predictive value of 93 %. ConclusionBoth pMN and non-pMN patients presented grey-zone PLA2R-ELISA results. It was necessary to perform PLA2R-IIF to assist in the diagnosis of patients with PLA2R-ELISA grey-zone results.
Read full abstract