Age- and sex-specific pediatric reference intervals: study design and methods illustrated by measurement of serum proteins with the Behring LN Nephelometer

We analyzed blood from 450 healthy children and adolescents, ages one to 19 y, as well as term and preterm infants, to define age- and sex-specific reference intervals for numerous blood constituents. Reference intervals were derived by using nonparametric methods to determine the 0.025 and 0.975 fractiles. Ten serum proteins were measured with the Behring LN Nephelometer. Girls over 10 years of age had higher concentrations of ceruloplasmin and alpha 1-antitrypsin than other children had. There was no sex-related difference in reference intervals for the other proteins tested. Reference intervals are presented for immunoglobulins G, A, and M, complement fractions C3c and C4, ceruloplasmin, transferrin, alpha 1-antitrypsin, retinol-binding protein, and prealbumin (transthyretin).