C3 and immunoglobulin G4-related sclerosing disease: In the age- and sex-adjusted logistic regression analysis, male gender [vs. female, odds ratio (OR) 0.064, 95% confidence interval (CI) 0.006–0.644, P = 0.020] and serum C3 levels (OR 1.090, 95% CI 1.005–1.182, P = 0.039) were significant factors negatively and positively related to SI, respectively, in untreated patients with IgG4-RD (Table 3).