Paediatric reference values for total homocysteine, tryptophan, tyrosine and phenylalanine in blood spots

Abstract

Determining blood concentrations of the amino acids homocysteine, tryptophan, tyrosine and phenylalanine in children is of value in the clinical practice. Over the past decades, the use of blood spot samples to examine amino acid concentrations is increasing rapidly. In children, the use of blood spot samples is especially of relevance, as this method is much less invasive than venous blood sampling. Currently, no paediatric reference values for amino acids in blood spots are available. The aim of the current study was to establish reference values for blood spot concentrations of total homocysteine, tryptophan, tyrosine and phenylalanine in school-age children. Dried blood spots were obtained in a community sample of 104 healthy children, aged 6–12 years old (52% males). Blood spot concentrations of total homocysteine, tryptophan, tyrosine and phenylalanine were determined by positive electrospray liquid chromatography-tandem mass spectrometry. Parents of participants completed questions regarding demographic characteristics. Our sample consisted of healthy children from various ethnic backgrounds, with varying levels of socioeconomic status, in line with the composition of the Dutch society. Blood spot concentrations of total homocysteine, tryptophan, tyrosine and phenylalanine were similar in males and females, and independent of age. In conclusion, paediatric reference values for blood spot concentrations of total homocysteine, tryptophan, tyrosine and phenylalanine were established, which could be of use in the clinical practice.

Keywords:

• Amino acids
• clinical practice
• school-age children
• screening

Acknowledgements

The authors would like to thank Ulbe Holwerda and Rob Kok (VU University Medical Center Amsterdam) for analyzing the blood spots. We are also grateful to all children and parents who participated in our study, as well as to our research assistants for their help in the data collection.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Additional information

Funding

This work was funded by Stichting Achmea Gezondheidszorg, [SAG-project Z329].