Diagnostic Study Of Serum Anti - M - Type Phospholipase A2 Receptor (PLA2R) Antibody - Negative Idiopathic Membranous Nephropathy

Object1、To evaluate the prevalence of serum anti-THSD7A (Thrombospondin type-1 domain-containing 7A) antibodies, anti-SOD2 (Manganese superoxide dismutase) antibodies, anti-a ENO (Alpha-enolase) antibodies in IMN (idiopathic membranous nephropathy) patients with negative anti-PLA2R (M-type phospholipase A2 receptor) antibodies. To evaluate the value of these three markers in the differential diagnosis of IMN and other glomerular diseases other than MN. To estimate the clinical significance of these autoantibodies in IMN patients with negative serum anti-PLA2R-antibodies.2、To evaluate the PLA2R antigen expression in renal tissue and to estimate the value of PLA2R antigen in the differential diagnosis of IMN and other glomerular diseases other than MN.MethodIn the study of serum antibodies, we use ELISA kit to detect sera anti-THSD7A antibodies, anti-SOD2 antibodies and anti-a ENO antibodies of patients who underwent renal biopsy at Peking Union Medical College Hospital from October 2013 to May 2015 and were diagnosed with IMN, SMN and other glomerular diseases. In this prospective study, we estimated the value of these three markers in the differential diagnosis of IMN and other glomerular diseases other than MN and the clinical significance of these autoantibodies in IMN patients with negative serum anti-PLA2R-antibodies.In the study of renal tissue PLA2R antigen, we used immunofluorescence to detect the PLA2R antigen expression in the frozen sections of patients who underwent renal biopsy at Peking Union Medical College Hospital from October 2013 to May 2015 and were diagnosed with IMN, SMN and other glomerular diseases. We evaluated the prevalence of PLA2R antigen positively expression in different diseases and the sensitivity, specificity, positive and negative predictive values, agreement rates to the differential diagnosis of IMN and other glomerular diseases.ResultsWe consecutively recruited 97 IMN patients with negative anti-PLA2R antibodies,31 IMN patients with positive anti-PLA2R antibodies,17 patients with SMN,28 patients with primary glomerular diseases other than MN and 40 healthy controls. ELISA kits were used to assay serum autoantibodies against THSD7A. We found 4 IMN patients were serum anti-THSD7A antibodies positive. Serum anti-THSD7A antibodies were of high specificity for IMN but the sensitivity is low because of the low serum positive rate in population. Of particular note was that we found one IMN patient with both serum anti-THSD7A antibodies and anti-PLA2R antibodies positive, which has never been reported in the world.We randomly selected 68 IMN patients with negative anti-PLA2R antibodies,21 IMN patients with positive anti-PLA2R antibodies,10 patients with SMN,28 patients with primary glomerular diseases other than MN, and 34 healthy controls from the subjects mentioned before. ELISA kits were used to assay serum autoantibodies against SOD2 autoantibodies and a ENO autoantibodies. We found serum autoantibodies-positive cases in all these four groups. Although there seemed to be a trend that autodantibodies positive rates are higher in IMN group compared to other glomerular diseases, the P value for X square test is more than 0.05.In IMN patients with negative anti-PLA2R antibodies, patients absent of anti-THSD7A, anti-SOD2, and anti-αENO antibodies had lower serum creatinine, higher eGFR and higher serum albumin(all P<0.05) at baseline and shorter duration for partial remission(P<0.05) as compared with IMN patients with at least one positive above-mentioned antibodies.In the study of renal tissue PLA2R antigen expression, we included 75 patients.48 IMN patients were included, the positive rate for serum anti-PLA2R antibodies was 52.1% and for tissue PLA2R antigen was 81.3%. In the differential diagnosis of IMN, SMN and other glomerular diseases, the specificities were more than 90% and agreement rates were more than 80%.Conclusion1、Anti-THSD7A antibodies are specific serum markers for IMN.2、Although the diagnostic significances for anti-SOD2 and anti-αENO antibodies are limited, in IMN patients with negative anti-PLA2R antibodies, absence of anti-THSD7A, anti-SOD2, and anti-aENO antibodies indicates milder clinical manifestation and shorter duration for partial remission.3、Sensitivity for detecting renal PLA2R antigen expression is higher than serum anti-PLA2R antibodies. Detection of renal PLA2R antigen has good sensitivity and specificity in the diagnosis of IMN. Suspected IMN patients especially for patients whose serum is negative for anti-PLA2R antibodies, renal PLA2R antigen detection might be taken into consideration.