[Expanded newborn screening in the Region of Murcia, Spain. Three-years experience]

The early detection of inborn errors of metabolism by mass spectrometry allows expanding the traditional neonatal screening of phenylketonuria and congenital hypothyroidism to test for aminoacidopathies, fatty acid oxidation disorders and organic acid metabolic disorders. Cystic fibrosis and biotinidase deficiency screening is implemented in the Region of Murcia. The aim of the study is to describe our experience in the expanded neonatal screening and to define the prevalence of each of the metabolic disorders early detected.

Since March 2007 until October 2010, a total of 71,595 neonates were screened with this expanded program by mass spectrometry, fluoroimmunoassay or colorimetric methods.

Thirty-eight patients (prevalence 1:1,884) were diagnosed of inborn errors of metabolism by mass spectrometry, 13 patients of cystic fibrosis (prevalence 1:5,507), 38 of congenital hypothyroidism (prevalence 1:1,884) and one of biotinidase deficiency. To date, the global frequency of inborn errors of metabolism is estimated to be 1:804. The positive predictive value for the results obtained by mass spectrometry was 20.25%. Two false negative patients were not identified (cystic fibrosis and methylmalonic aciduria patients) and 6 non neonatal patients were detected through expanded neonatal screening.

Our data support the necessity of unifying the set of metabolic diseases to be screened in all Regions of Spain for early detection of a defined panel of inborn errors of metabolism and to provide every newborn the same opportunities to be early diagnosed.