There was no significant association between C3 polymorphism and CKD progression by Cox regression analysis, hazard ratio (HR) = 1.1(95% confidence interval (CI) 0.75–1.6; p = 0.59)for C3FF, HR = 1.0(CI 0.8–1.3; p = 0.78) for C3FS and HR = 0.95(CI 0.74–1.2; p = 0.70) for C3SS. The factors which showed significant association with progression in our CKD cohort in multivariate Cox regression analysis were age, gender, smoking, haemoglobin, baseline eGFR, and urinary protein:creatinine ratio (S5 Table). Here, C3 is linked to chronic kidney disease.