Pediatric reference intervals for plasma and urine essential amino acids in a Turkish population.

Objective: To establish age- and sex-specific reference intervals for essential amino acids in a healthy Turkish pediatric population.

Methods: A total of 945 clinically healthy children (531 boys and 414 girls, ranging in age from birth to 14 years) were enrolled. Plasma and urine amino acids' concentrations were measured by high-performance liquid chromatography.

Results: Concentrations of essential amino acids in plasma were higher in girls than in boys in the age groups of 0-1 months and 7-14 years; however, there was no difference in the other age groups. Concentrations of essential amino acids in urine were higher in girls than in boys in the age group of 0-1 months; however, there was no difference in the other age groups. Our results demonstrated the sex-related differences in concentrations ofleucine, isoleucine, valine, phenylalanine, lysine, and histidine in plasma, which increased with age in boys but not in girls. The concentrations of leucine, tryptophan, methionine, and lysine in urine declined with age in girls but not in boys, which were sex-related differences, too.

Conclusions: We defined essential amino acids' reference intervals in a Turkish pediatric population.