Age-specific reference intervals for serum IgG, IgA, and IgM in healthy Brazilian children and adolescents

Serum immunoglobulin reference intervals vary by age, ethnicity, and environment, limiting the clinical utility of international guidelines for Brazilian pediatric patients. This study established age-specific reference intervals for serum IgG, IgA, and IgM concentrations in healthy Brazilian children and adolescents, focusing on defining precise trajectories across distinct developmental stages.

Serum samples from 2,911 healthy individuals aged 1 month to 17 years were analyzed. Serum IgG, IgA, and IgM concentrations were measured by rate immunoturbidimetry standardized against international reference materials and evaluated using percentile-based analyses and quantile regression modeling across age-stratified cohorts.

Immunoglobulin concentrations varied substantially across age groups. Median IgG levels increased from 3.65 g/L (2.5th percentile: 2.25 g/L) at 1-3 months to 11.66 g/L (2.5th percentile: 7.69 g/L) at 13-17 years, with parallel age-related increases observed for IgA and IgM. The most pronounced changes occurred during infancy. Although early-life immunoglobulin dynamics did not entirely align with traditional trajectories, they suggested population-specific variations in humoral immune maturation.

This study establishes the first comprehensive, population-specific reference intervals for serum immunoglobulins in Brazilian youth from early infancy through adolescence. By documenting unexpected deviations from traditional early-life trajectories, our study provides a critical benchmark for Brazilian pediatric care and a model framework for Latin American populations.