Immunoglobulin G and immunoglobulin G subclass concentrations differ according to sex and race

Serum immunoglobulin G (IgG) concentrations are integral to the workup of immune deficiencies and IgG4-related disease (IgG4-RD). Demographic differences in IgG concentrations are poorly described but can influence test interpretation, contribute to racial disparities in primary immunodeficiency diagnosis, and explain demographic differences in IgG concentrations in IgG4-RD.

To assess differences in IgG and IgG subclass concentrations according to sex and race.

We identified patients with IgG and IgG subclass concentrations measured in a large health care system. Multivariate-adjusted differences in IgG and IgG subclass concentrations and the proportion of subjects with results outside of reference ranges according to sex and race were estimated.

Of the 12,851 patients, the mean age was 54.7 years and 7917 (62%) were female. Of these, 11,673 (91%) were white, 611 (5%) were black, and 302 (2%) were Asian. Compared with the mean concentrations of white patients, Asian and black patients had higher mean concentrations of IgG (1340.0 and 1504.4 vs 988.1 mg/dL, P < .001), IgG1 (782.0 and 938.4 vs 592.4 mg/dL, P < .001), IgG2 (493.5 and 384.2 vs 305 mg/dL, P < .001), IgG3 (76.6 and 91.9 vs 55.9 mg/dL, P < .001), and IgG4 (140.4 and 53.6 vs 41.6 mg/dL, P < .001). Immunoglobin G subclass 4 concentrations were higher in males than those in females (56.3 vs 37.4 mg/dL, P < .001). Similar observations were made when comparing the proportions of patients with results outside of reference ranges and after stratifying by diagnosis.

Immunoglobin G and IgG subclass concentrations differ according to sex and race. These findings may have implications for the interpretation of these test results but require confirmation in diverse, healthy populations.