Clinical research of fractional excretion of IgG on predicting drug responsiveness in patients with idiopathic membranous nephropathy

Abstract

Objective To explore the predictive value of fractional excretion of IgG (FE IgG) on drug responsiveness and remission in patients with idiopathic membranous nephropathy (IMN). Methods Retrospective analysis of 82 patients with IMN diagnosed by clinical and pathological data and regularly followed up from April 2014 to August 2017. Receiver operating characteristic (ROC) curve was used to determine the FE IgG threshold. Comparing the difference of remission time under different baseline levels of FE IgG, and analyzing the effect of different levels of FE IgG on the drug responsiveness of immunosuppressive therapy (tacrolimus or cyclophosphamide) and supportive therapy. Results Areas under the curve (AUC) of estimated glomerular filtration rate (eGFR), 24-hour urinary protein quantity and FE IgG were 0.509, 0.701 and 0.948, respectively. Before treatment, there was no significant difference in gender, age, mean arterial pressure and eGFR between the high FE IgG group (FE IgG>0.029) and low FE IgG group (FE IgG 0.05). The remission time of high FE IgG group was (18.75±6.81)months, while it was (8.46±3.74)months in low FE IgG group, with significant difference (P<0.01). There was no difference in remission time of immunosuppressive therapy and supportive therapy in low FE IgG group (P=0.265), bo-th of which were lower than the high-level immunosuppressive therapy group (P<0.001). The remission time of tacrolimus was shorter than that of cyclophosphamide in high FE IgG group, but with no significant difference (P=0.131). There was significant difference in the remission time of tacrolimus between the high and low level groups of FE IgG (P<0.01). Under electron microscope, the ratio of foot process fusion and podocyte diffuse vacuolar degeneration in the high level group of FE IgG was higher than that in the low level group (P<0.01). Conclusions FE IgG can be used as a clinical indicator for predicting drug responsiveness and remission in patients with IMN, and is essential for early identification of high-risk patients and for making clinical decisions. Patients with high FE-IgG may benefit from early initiation of immunosuppressive therapy. Key words: Immunoglobulin G; Renal elimination; Remission time; Urinary protein; Idiopathic membranous nephropathy