Age-Specific Reference Values for Amino Acid Content in Dried Blood Spots in Children in Western Kazakhstan, Measured by Tandem Mass Spectrometry

Abstract

Measuring the level of amino acids in the blood is one of the stages in the early diagnosis of inborn errors of metabolism (IEM), implying timely initiation of therapeutic measures. Tandem mass spectrometry (MS/MS) is now replacing traditional IEM screening methods. Dried blood spot amino acid reference values developed for the pediatric population are crucial for interpreting test results and diagnosing aminoacidopathies. The study aims to establish reference values for amino acid (AAs) concentrations in samples of dried blood spots from newborns in Western Kazakhstan using LC-MS/MS (liquid chromatography-tandem mass spectrometry) technology. Methods: The cross-sectional study included 250 healthy newborns of Western Kazakhstan aged 1-3 days, born at term and breastfed, 49.2% male and 50.2% female. To establish the age-specific reference values for AAs, newborns were divided into three groups: (1) 1 day, (2) 2 days, and (3) 3 days. Blood samples on Guthrie cards were collected on days 1–3 of life and quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Nonparametric statistical approaches were used to generate the 2.5th–97.5th percentile distributions for newborns. Results: 3 of the 15 DBS amino acid distributions were dependent on gender. There was a statistically significant difference in the mean level of alanine, citrulline, and glutamic acid in males and females. The highest values were determined in the female group. Age-related differences in glutamic acid, leucine, ornithine, tyrosine, and valine concentration levels were observed. No significant correlations were found between the concentrations of 15 amino acids in dried blood spots and the body weight of newborns. Conclusion: The present study established amino acid concentrations that can be utilized as reference standards in Kazakhstan's newborn screening program for inherited metabolic diseases.