Cuban neonatal screening of phenylketonuria using an ultramicro-fluorometric test

BackgroundGuthrie's bacterial inhibition assay was used in Cuba, since 1983. A decentralized program for the newborn screening of hyperphenylalaninemias started in the year 2000 using an ultramicro-fluorometric test (UMTEST PKU).MethodsA simple and rapid ultramicro-fluorometric test based on McCaman and Robin's method has been designed, developed and applied for the measurement of Phe in dried blood spots on filter paper.ResultsThe UMTEST PKU exhibited an acceptable precision and accuracy. Samples of 27 528 newborns on filter paper Schleicher & Schuell 903 (S&S 903) from the National neonatal screening program were collected and analyzed, and the mean Phe concentration was 66.5 µmol/l. Our assay showed high Pearson and concordance correlations with 2 commercially available kits. A total of 521 923 Cuban newborns were studied from the year 2000 to 2007 using the UMTEST PKU. Elevated blood phenylalanine levels were found in 1764 infants (0.34%) and no false negative were noted. Ten cases were diagnosed with phenylketonuria, all of them with an initial phenylalanine concentration over 360 µmol/l.ConclusionsThe analytical performance characteristics of our assay and its use in the National program have demonstrated its suitability for the neonatal screening of PKU.