Reference intervals for serum immunoglobulin A, G, and M in a Danish paediatric population-based cohort

Objectives: To determine age- and sex-specific reference values for serum immunoglobulins (IgA, IgG, and IgM) in a population-based cohort of 6 to 18 years old Danish children and adolescents and investigate if immunoglobulin concentrations vary with body mass index standard deviation score (BMI SDS). Materials and methods: A total of 2171 school children and adolescents (median age 12.0 years) were recruited. BMI SDS was calculated, and health status was assessed by questionnaire and blood samples. Fasting serum concentrations of IgA, IgG, and IgM were determined by immunonephelometry. Sex- and age-specific percentiles were generated and partitioned following the Clinical and Laboratory Standards Institute (CLSI) EP28-A3c guidelines. Multiple linear regression models were used to investigate associations between IgA, IgG, IgM, and BMI SDS adjusted for age and sex. Results: Concentrations of IgA increased with age but did not differ between boys and girls. An age-dependent increase was also detected for concentrations of IgG and IgM, although for IgG it was more pronounced in boys than girls. Girls had higher concentrations of IgG and IgM than boys at all ages. Concentrations of IgM were inversely associated with BMI SDS independent of age and sex. Conclusions: We generated age- and sex-specific reference intervals for IgA, IgG, and IgM based on children and adolescents from a Danish/North-European Caucasian population-based cohort. The findings can help evaluate alterations seen in primary and secondary immunodeficiencies and autoimmune diseases.