Neonatal screening for inborn errors of metabolism using tandem mass spectrometry

Background. As part of our neonatal screening program we applied tandem mas s spectrometry on 128.225 dried blood samples for detection of inborn error s of metabolism. Results. Eleven patients with phenylketonuria and three patients with hyper phenylalaninemia were detected. Tyrosinemia and citrullinemia were found in one and four newborns, respectively. Analysis of free carnitine and acylca rnitines resulted in the diagnosis of medium chain acyl-CoA dehydrogenase ( MCAD) deficiency in 17 newborns. Other detected defects of fatty acid oxida tion were long-chain-3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency (tw o cases) and the defect of the trifunctional protein tone case). Each, isov aleric 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 me ters mea su red by tandem mass spectrometry was 0.38%. This was significant ly 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.