C3 and Hematuria: As presented in Table 2, compared with the non-IgAN group patients in the training cohort, the IgAN group patients were significantly younger on average, had a higher incidence of hematuria and hypertension, and had higher levels of serum albumin, urea nitrogen, creatinine, uric acid, IgA, IgG, and IgA/C3 ratios (P < 0.01).