ABSTRACT
Abstract Neonatal screening in Colombia has been carried out since 2000. The problem that most concerns is the absence of expanded screening. To stablish reference values for amino acids and acylcarnitines, in order to provide information to guide the implementation of expanded screening. Samples collected on Whatman 903 filter paper from 10284 newborns were processed by Tandem Mass Spectrometry System (Waters - Perkin Elmer), and the NeoBase™ non-derivatized MS/MS kit (PerkinElmer), which contains controls for 11 amino acids, and 31 acylcarnitine species. For each analyte the upper limit was set above the 99th percentile, while the lower limit was set below the 1st percentile. Comparison of full-term newborn amino acid concentrations with premature ones showed no significant differences in three of them: Glycine p-0.99574, Ornithine p=0.35274, Phenylalanine p=0.13499, neither in levels of 11 of the 31 acylcarnitines. Comparison of analyte concentrations in this study with previous reports showed significant differences for all amino acids and acylcarnitines (<0.05). Experience was gained in the pre-analytic stage of expanded screening and reference values were established, for the implementation of neonatal screening program in the country.