title: Establishment of reference range of plasma amino acids for younger Chinese children by reverse phase HPLC.
abstract: BACKGROUND
  Due to lack of country-specific norms in China, we established the reference range of plasma amino acids for younger Chinese children by reverse phase high-performance liquid chromatography (HPLC).
  
  
  METHODS
  Plasma proteins were precipitated with ethanol. L-Norvaline served as an internal standard. This HPLC method was based on automated precolumn derivatization using o-phthalaldehyde 3-mercaptopropionic acid for primary amino acids and 9-fluorenylmethyl chloroformate for secondary amino acids. Twenty-three amino acid derivatives were separated by a Zorbax Eclipse AAA column and detected fluorometrically. Plasma amino acids were measured in 108 healthy Chinese children (ages 0-5 years, 59 boys and 49 girls).
  
  
  RESULTS
  The assay was linear from 7.2 to 925.0 micromol/L for all amino acids. Recovery of amino acids added to plasma samples was 93%-107%. Within- and between-run reproducibility was 0.18%-6.27% and 2.94%-16.15%, respectively. Sex- and age-specific plasma amino acid reference range for younger Chinese children was established. In our study, the boys had significantly higher levels of glutamine, citrulline, and tryptophan than girls (p < 0.05), and the girls had a significantly higher level of alanine than boys (p < 0.05). Compared with the 0- to 1-year group, the 1- to 5-year group had significantly higher levels of citrulline, valine, phenylalanine, isoleucine, and sarcosine and lower levels of aspartate, glutamate, serine, threonine, alanine, methionine, and tryptophan (p < 0.05).
  
  
  CONCLUSIONS
  This study validates the HPLC method described here as a simple, rapid, and reliable assay. The reference range of plasma amino acids for younger Chinese children is different from that for Caucasian children and will facilitate our clinical diagnosis in the future.
authors.affiliation: Department of Endocrinology and Metabolism, Guangzhou Women and Children's Medical Center, Guangzhou Medical College, Guangzhou, Guangdong, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Yi
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Huifen
authors.initials: H
authors.lastname: Mei
authors.forename: Fangling
authors.initials: F
authors.lastname: Zeng
authors.forename: Zhijian
authors.initials: Z
authors.lastname: Huang
authors.forename: Huilin
authors.initials: H
authors.lastname: Niu
mesh_terms: D000596:Amino Acids / Q000097:blood*; D044466:Asian People; D002624:Chemistry, Clinical / Q000592:standards*; D002675:Child, Preschool; D002681:China; D002851:Chromatography, High Pressure Liquid / Q000592:standards*; D056148:Chromatography, Reverse-Phase / Q000592:standards*; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012016:Reference Values
chemical_list: D000596:Amino Acids