Normal Plasma Free Amino Acid Levels in Thai Children
JISNUSON SV ASTI, Ph.D.*,**,
PORNSWAN WAS ANT, M.D.***,
MONTIP TIENSUW AN, Ph.D.*****,
PHANNEE SA WANGAREETRAKUL, M.Sc. *,
CHANTRAGAN SRISOMSAP, Ph.D.*,
SUTHIPONG PANGKANON, M.D.****,
KANOKPORN BOONPUAN, M.Sc.*,
SOMPORN LIAMMONGKOLKUL, M.Sc. ***
Affiliation : * Laboratory of Biochemistry, Chulabhorn Research Institute, Bangkok 10210,
**Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok 10400,
***Department of Pediatrics, Siriraj Hospital, Mahidol University, Bangkok 10700,
**** Queen Sirikit National Institute of Child Health, Ministry of Public Health,
*****Department of Mathematics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
AbstractAnalysis of plasma free amino acid levels is important for diagnosis of inborn errors of
metabolism. Traditionally, this is performed using commercially available dedicated amino acid
analyzers, but few such instruments are available in Thailand, and many are not used in routine
operations. Here, the authors describe the analysis of plasma free amino acid levels in 57 normal
children by reverse-phase HPLC and pre-column derivatization with phenylisothiocyanate. Plasma
free amino levels are reported as mean ± SD and 95 per cent confidence interval of mean for
each of 5 age groups: 0-6 months; 6-12 months; 1-3 years; 3-6 years; 6-12 years. Mean amino
acid levels were generally similar in all age groups (p2!0.01), except that hydroxyproline tended to
be higher in the 0-6 months age group compared to other age groups (p<0.01).
Comparisons were made between the present data with the normal free plasma amino acid
levels in children of similar age groups reported both in Thailand and overseas in terms of both
mean ± SD and maximum and minimum values. Overall, our methodology involving HPLC can
identify 35 amino acid derivatives, including all the major amino acids except for cysteine, which
is substantially more than the number reported in earlier work on plasma free amino acid levels in
normal Thai children. Moreover, the present methodology gives mean ± SD values similar to an
overseas report. For these reasons, HPLC should be considered as an alternative approach in
laboratories, where demand does not justify the need for dedicated amino acid analyzers. However,
there can be substantial variations between the results from different laboratories, and each labora-
tory should establish its own normal values.
Keywords : Amino Acid, Inborn Error, Plasma
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