AGE-SPECIFIC DISTRIBUTION OF PLASMA AMINO-ACID-CONCENTRATIONS IN A HEALTHY PEDIATRIC POPULATION

Reference values were determined for 23 plasma free amino acids from m easurements done in 148 healthy children ranging from 0 to 18 years of age. Amino acid analysis was performed by ion-exchange chromatography . We propose a graphic form of presenting the age-specific distributio n of plasma amino acid concentrations where the 10th, 50th, and 90th q uantiles are illustrated. Although each amino acid possesses its own p attern of distribution, we can identify five different profiles. Nine amino acids (alanine, arginine, asparagine, methionine, ornithine, phe nylalanine, proline, threonine, and tyrosine) demonstrate a decrease i n their concentrations during the first year of life; their concentrat ions then tend to increase throughout childhood and adolescence. Nine others (cystine, glutamine, glycine, histidine, isoleucine, leucine, l ysine, tryptophan, and valine) show a steady increase throughout infan cy, childhood, and adolescence. Five amino acids (aspartic acid, citru lline, glutamic acid, serine, and taurine) do not follow these two com mon profiles. For the first time, quantile curves are produced to illu strate the age-dependent variation of amino acid concentrations from i nfancy to adulthood. This alternative way of presenting amino acid con centrations may facilitate the follow-up of patients with inborn error s of amino acid metabolism.