RESUMO
BACKGROUND: Guthrie'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). METHODS: A 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. RESULTS: The UMTEST PKU exhibited an acceptable precision and accuracy. Samples of 27528 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 micromol/l. Our assay showed high Pearson and concordance correlations with 2 commercially available kits. A total of 521923 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 micromol/l. CONCLUSIONS: The analytical performance characteristics of our assay and its use in the National program have demonstrated its suitability for the neonatal screening of PKU.
