Newborn screening for very-long-chain acyl-CoA dehydrogenase (VLCAD) deficiency, a type of long-chain fatty acid oxidation disorder (LCFAOD), can effectively identify infants who show no symptoms, according to a study published in the journal Molecular Genetics and Metabolism Reports

“Our cohort showed that elevation of C14:1/C12:1 was informative in discriminating affected from unaffected individuals and contributes to improve the accuracy of confirmatory testing of infants with presumptive positive for VLCAD deficiency,” the authors wrote.

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Their aim was to describe the biochemical and molecular characteristics and diagnostic outcomes of patients with VLCAD deficiency identified through newborn screening using tandem mass spectrometry.

The team compared the acylcarnitine profiles in dried blood spot of newborns. The researchers analyzed levels of C14, C14:1, C14:2, and the ratio of C14:1/C12:1 in the dried blood spots. They also analyzed these in the plasma of true positive and false positive patients.

The results showed that the presence of compound heterozygous or homozygous pathogenic variants together with high levels of C14, C14:1, and C14:1/C12:1 was able to identify 19 patients with VLCAD deficiency. All of these patients were asymptomatic. 

The researchers said that the C14:1/C12:1 ratio in newborn dried blood spots and the plasma acylcarnitine profiles at follow up were the most useful markers differentiating between true and false positive cases. 

Of all patients for whom molecular analysis data was available, more than half (56.7%) had a single pathogenic mutation in the ACADVL gene. Lymphocyte enzyme analysis was uninformative in 23% of the analyzed cases.

“C14:1/C12:1 is a precise diagnostic marker of VLCAD deficiency, which was consistent with previous studies,” the researchers concluded.


Upadia J, Noh G, Lefante JJ, Andersson HC. Biochemical and molecular characteristics among infants with abnormal newborn screen for very-long-chain acyl-CoA dehydrogenase deficiency: a single center experience. Mol Genet Metab Rep. Published online August 25, 2023. doi:10.1016/j.ymgmr.2023.101002