The establishment of biological reference intervals of immunoglobulin in serum for children in Changchun

Objective To establish the biological reference intervals of serum immunoglobulin (Ig) for children (neonates to young adults) in our laboratory. Methods This was a retrospective study. Serum IgG, IgA and IgM of the neonatal (1–28 days) to 18 years old who visited the First Hospital of Jilin University during January 2011 to July 2014 were measured. The inclusion criteria were normal C–reactive protein content, normal liver and kidney function and without history of chronic diseases, allergic reactions, connective tissue diseases, rheumatic diseases and human immunodeficiency diseases. Children whose Ig tests were below upper limit of adult reference range were divided into 19 age groups. By eliminating outliers within each group, 9 466 cases of reference individuals conformed to the establishment of reference intervals were selected. Rank sum test was applied in comparing Ig levels of each two adjacent age groups, if there was not statistical significance (P>0.05), the two age groups were merged; otherwise not merged. The upper and lower limit of Ig reference range for each age group were calculated using nonparametric method, and biological reference intervals of children's serum Ig were established. Results The neonatal serum IgG decreased grually after birth and reached the lowest point at 29 days–3 months, then the concentration increased gradually along with age growth and reached adult level by 11 years old. Neonatal serum IgA and IgM levels were at the lowest point and the concentration increased along with age growth then reached adult levels by 11 and 2 years old respectively. The children's serum Ig reference intervals were as below: IgG: 3.59–7.90, 2.26–5.40, 2.72–6.62, 2.87–7.74, 3.38–8.07, 3.80–9.08, 4.86–11.40, 4.97–11.70, 5.51–12.40, 6.17–13.10, 6.41–13.60, 6.53–14.20 and 6.84–14.30 g/L for neonatal, 29 days–3 months, 4–6 months, 7 months, 8–9 months, 10 months–1 year old, 2, 3, 4, 5–6, 7, 8 and 9–10 years old, respectively; IgA: 0.23–0.45, 0.24–1.02, 0.23–0.79, 0.23–0.92, 0.24–1.03, 0.24–1.56, 0.26–1.93, 0.31–2.16, 0.44–2.56, 0.56–2.85, 0.52–3.35 and 0.63–3.23 g/L for neonatal–3 months, 4 months, 5–7 months, 8–9 months, 10 months –1 years old, 2, 3, 4, 5–6, 7, 8, and 9–10 years old, respectively; IgM: 0.16–0.70, 0.21–1.20, 0.30–1.62, 0.38–2.16 and 0.44–2.17 g/L for neonatal, 29 days–3 months, 4–7 months, 8–9 months and 10 months–1 years old, respectively. Conclusions There were great differences of the serum Ig concentrations between children and adults, thus children's immunologic function should not be assessed based on adult Ig reference intervals. According to the research, reference intervals of Ig were obtained for children at different age groups in the laboratory and reference in evaluating children's immunologic function was provided for clinicians. (Chin J Lab Med, 2015, 38: 191–195) Key words: Immunoglobulin; Child; Reference value