The relationship of race, sex, and age to concentrations of serum immunoglobulins expressed in international units in healthy adults in the USA.

Only a few investigations have been made to obtain human serum immunoglobulin values in units compatible with those used by the WHO International Reference Preparation for the Human Immunoglobulins IgG, IgA, and IgM. We report our summary statistics of serum IgG, IgA, and IgM, in international units (IU), for some 800 healthy American adults grouped by age, sex, and race. Our findings are in general agreement with some, but not with all, published data. We found that the mean IgG concentration is markedly higher and the mean IgA concentration is slightly higher in blacks than in whites. Except for white females, there was a significant increase in mean IgA with age for both races. In the younger adults of both races, mean IgM values were markedly higher in females than in males. Statistically significant interactions between race, age, and sex factors were seen for all three immunoglobulin classes. Although we have attempted to estimate the normal population means and variances for the serum concentration of IgG, IgA, and IgM the process we used to select specimens may have resulted in some bias; much larger, truly randomized, and fully documented studies in different geographic areas and in different socioeconomic and racial groups are needed to provide accurate acceptable limits for human immunoglobulins.