Fluctuations and Determinants of Amino Acids and Acylcarnitine Species in Newborn Screening by Tandem Mass Spectrometry

OBJECTIVES: To evaluate the stability of amino acid and acylcarnitine species concentrations in newborn screening and identify factors influencing their variations. METHODS: Tandem mass spectrometry screening was performed on 270,791 neonates. Coefficients of variation were calculated, monthly trends analyzed, and seasonal fluctuation reasons explored. RESULTS: Arginine and methionine showed the highest coefficients of variation (28.3% and 13.6%), with distinct seasonal variation-lower in summer and higher in winter, negatively correlated with temperature and humidity. CONCLUSIONS: In tandem mass spectrometry-based newborn screening, Arginine and methionine show poor stability with seasonal concentration fluctuations. Establishing season-specific cutoffs may reduce false positives and missed detections.