Neonatal screening for inborn errors of metabolism using tandem mass spectrometry

Background. As part of our neonatal screening program we applied tandem mass spectrometry on 128.225 dried blood samples for detection of inborn errors of metabolism. Results. Eleven patients with phenylketonuria and three patients with hyperphenylalaninemia were detected. Tyrosinemia and citrullinemia were found in one and four newborns, respectively. Analysis of free carnitine and acylcarnitines resulted in the diagnosis of medium chain acyl-CoA dehydrogenase (MCAD) deficiency in 17 newborns. Other detected defects of fatty acid oxidation were long-chain-3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency (two cases) and the defect of the trifunctional protein tone case). Each, isovaleric acidemia and 3-methylcrotonyl-CoA carboxylase deficiency were found in four individuals, which may indicate a considerably higher incidence of these diseases than previously reported. The reca II rate for a II pa ra meters mea su red by tandem mass spectrometry was 0.38%. This was significantly lower than the recall rate of 0.5% for PKU screening alone prior to the introduction of the new technique. Conclusion. We expect tandem mass spectrometry to be used in many neonatal screening laboratories in the near future.