C3 and chronic kidney disease: Cox regression showed a significant association between C3 polymorphism and CKD progression in the IgAN group with HR = 1.9 (95% CI 1.1–3.1; p = 0.018) for heterozygous C3FS, increasing further for homozygous C3FF to HR = 2.8 (95% CI 1.2–6.2; p = 0.014).