Harkness T, Fu X, Zhang Y, et al. - Researchers evaluated variations in immunoglobulin G (IgG) and IgG subclass levels by gender and race. A large healthcare system was used to select patients in whom IgG and IgG subclass concentrations were measured. Asian and Black patients vs White patients were found to have higher mean levels of IgG (1340.0 and 1504.4 vs 988.1 mg/dL), IgG1 (782.0 and 938.4 vs 592.4 mg/dL), IgG2 (493.5 and 384.2 vs 305 mg/dL), IgG3 (76.6 and 91.9 vs 55.9 mg/dL), and IgG4 (140.4 and 53.6 vs 41.6 mg/dL). Higher IgG4 concentrations were detected in males vs females. Based on gender and race, differences were evident in IgG and IgG subclass concentrations. These observations may have implications for the interpretation of these test results.