Characteristic Findings of Infants with Transient Elevation of Acylcarnitines in Neonatal Screening and Neonatal Weight Loss

The detection of elevated long-chain acylcarnitine levels, particularly C14:1 and the C14:1/C2 ratio, during neonatal screening may indicate very-long-chain acyl-CoA dehydrogenase deficiency (VLCADD), although similar findings can result from postnatal starvation. We investigated the relationship between false-positive results, postnatal weight loss, and subsequent growth. Additionally, we explored potential diagnostic markers of postnatal starvation. The following neonates from Oita Prefecture (April 2014-March 2024) were included in this study: patients identified as false-positive for VLCADD (<i>n</i> = 19), patients with VLCADD (<i>n</i> = 3), and children negative in mass screening who completed their 3-year-old health check-up (<i>n</i> = 30). The false-positive group exhibited significant weight loss at blood sampling for neonatal screening. An acylcarnitine analysis showed significant increases in various short- to long-chain fatty acids in the false-positive group, likely owing to enhanced fatty acid catabolism via β-oxidation. Elevation of a broad range of fatty acids and reduced amino acid levels seemed to be associated with significant weight loss at blood sampling.