A pilot study of neonatal screening by electrospray ionization tandem mass spectrometry in Taiwan.

Amino acid and acylcarnitine profiling of dry blood specimens using electrospray tandem mass spectrometry (ESI/MS/MS) has been recognized as an useful tool for screening inherited metabolic defects of newborns. In this pilot study, we introduced this technology to screen 2100 newborns to establish the normal amino acid and acylcarnitine level. Based on the upper cutoff level (average + 4*SD), twenty-nine samples studied were considered as abnormal. After follow-up samples and urine GC/MS analysis, only two were confirmed as true inborn errors. One was identified as hyperphenylalaninemia, and the other as isovaleric acidemia. The positive rate of true inborn metabolic error was 0.09% (2/2100), and the false positive rate 1.28% (29/2100) in this study. ESI/MS/MS is proven to be an adequate tool for inborn metabolic error screening.