Elevated baseline serum IgA may predict earlier proteinuria remission in IgA nephropathy patients

The goals of this work were to investigate the correlations of elevated serum IgA with renal pathology and outcome of proteinuria in IgA nephropathy patients. Retrospective cohort analysis enrolled 90 IgA nephropathy patients (proteinuria ≥0.5 g/24 hr, estimated glomerular filtration rate (eGFR) ≥30 ml/min/1.73 m²) who were admitted to The Sixth Affiliated Hospital of Sun Yat-sen University from 2013.01 to 2017.04. The elevated serum IgA level was found in 20 (22.2%) patients. In clinical characteristics, serum IgG, ratio of IgA/C3 and recurrent mucosal infection rate were increased obviously in high serum IgA group compared with normal serum IgA group (serum IgG, 14.90±3.50 g/L vs. 10.27±3.49 g/L, P<0.001, IgA/C3, 4.45±1.21 vs. 2.77±0.75, P<0.001, recurrent mucosae infection rate, 40.0% vs. 14.3%, P=0.027). In kidney biopsy, mesangial proliferation was significantly more common in normal serum IgA group (81% vs. 50% in high serum IgA group, P=0.028). The proportion of crescent less than 25% more often occurred in elevated IgA group (81.3% vs. 63.8% in normal IgA group). The Kaplan-Meier curves showed that proteinuria remission rate for patients with high serum IgA was 80%, 85%, 90%, 95% and 95% after 3, 6, 9, 12 and 15 months compared with patients with normal serum IgA (proteinuria remission rate, 45%, 64%, 75%, 86% and 93%, P=0.020). Cox proportional hazard regression model indicated that elevated serum IgA (RR=1.984, P=0.040) and steroids therapy (RR=2.192, P=0.030) were independent predictors for proteinuria remission in IgA nephropathy patients. In view of our data, more active treatments may improve outcome of IgA nephropathy patients with elevated serum IgA. We conclude that elevated serum IgA may indicate a higher proteinuria remission rate within a shorter period of time in IgA nephropathy patients.