Immunoglobulin values in healthy Thai children aged ≤ 24 months determined by nephelometry.

BACKGROUND Variation of normal immunoglobulin (Ig) levels between different genetic and environment factors has been studied. Although antibody deficiency diseases can start from infancy, data of Ig reference levels in children aged ≤24 months are still limited, especially in Asian children. PURPOSE The aim of this study was to determine serum IgG, IgA, IgM, and IgG subclasses in healthy Thai children from the newborn period to age 24 months. METHODS Serum samples were collected from healthy Thai children age <1-24 months to measured serum IgG, IgA, IgM, and IgG subclasses by nephelometry. RESULTS Of the 100 infants, 44% were female with a median (range) age of 13 (0.3-24) months. The geometric mean IgG was 803 mg/dL, IgA 36 mg/dL, and IgM 102 mg/dL. The mean IgG1 was 646 mg/dL, IgG2 127 mg/dL, IgG3 45 mg/dL, and IgG4 17 mg/dL. The average ratios of IgG subclass 1:2:3:4 were 77:15:6:2%. No significant differences in each immunoglobulin isotype between genders were found. Our mean IgG level was slightly lower than that in healthy Thai children, measured by radial diffusion method but not significant except 1-3 months (p = 0.016). However, the mean IgG level in our study was higher than that reported by radial diffusion in healthy US children (p <0.001). CONCLUSIONS This study illustrated the importance of having normal Ig values from age- and ethnically-matched controls by high precision nephelometric assay in order to appropriately diagnose immunologic disorders in Asian infants.