Bi TD, et al. - In this retrospective study, researchers assessed serum C4 as a predictor of the prognosis of IgA nephropathy (IgAN) patients. A composite event of either a ≥ 50% decrease in estimated glomerular filtration rate or end-stage renal disease or mortality was considered as the primary endpoint. Overall 1356 IgAN patients were analyzed. Findings revealed significant correlations of serum C4 levels with clinical prognostic factors. A positive correlation of serum C4 levels with urinary protein excretion, as well as a negative correlation with the estimated glomerular filtration rate was observed. Furthermore, a rise in serum C4 levels was noted with the aggravation of tubulointerstitial injury, crescents and ratios of global sclerosis. Findings showed the utility of serum C4 as a predictor for the prognosis of IgAN patients.