title: Challenges for Worldwide Harmonization of Newborn Screening Programs.
abstract: Inherited metabolic disorders (IMDs) are caused by a defect in a metabolic pathway, leading to malfunctioning metabolism and/or the accumulation of toxic intermediate metabolites. To date, hundreds of IMDs have been identified. Many of these diseases are potentially fatal conditions that are not apparent at birth. Newborn screening (NBS) programs involve the clinical and laboratory examination of neonates who exhibit no health problems, with the aim of discovering those infants who are, in fact, suffering from a treatable condition.
  
  
  
  In recent years, the introduction of tandem mass spectrometry has allowed the expansion of screening programs. However, this expansion has brought a high degree of heterogeneity in the IMDs tested among different NBS programs. An attempt to harmonize the metabolic conditions recommended to be screened has been carried out. Two uniform screening panels have been proposed in the US and European Union, by knowledgeable organizations. Here, we review current evidence-based processes to assess and expand NBS programs. We also discuss the IMDs that have recently been introduced in some screening programs, such as severe combined immunodeficiencies, lysosomal storage disorders, and adrenoleukodystrophy.
  
  
  
  NBS programs have been an established public health function for more than 50 years to efficiently and cost-effectively identify neonates with severe conditions. However, NBS is not yet optimal. This review is intended to elucidate the current degree of harmonization of NBS programs worldwide as well as to describe the major controversial points and discuss the multiple challenges that must be confronted in expanded NBS strategies.
authors.affiliation: Metabolic Diseases Laboratory, Laboratory of Medicine, Department of Clinical Biochemistry, Hospital Universitario Central de Asturias, Oviedo, Spain. edumartinezmorillo@gmail.com.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Martínez-Morillo
authors.affiliation: Metabolic Diseases Laboratory, Laboratory of Medicine, Department of Clinical Biochemistry, Hospital Universitario Central de Asturias, Oviedo, Spain.
authors.forename: Belén
authors.initials: B
authors.lastname: Prieto García
authors.affiliation: Metabolic Diseases Laboratory, Laboratory of Medicine, Department of Clinical Biochemistry, Hospital Universitario Central de Asturias, Oviedo, Spain.
authors.forename: Francisco V
authors.initials: FV
authors.lastname: Álvarez Menéndez
mesh_terms: D020739:Brain Diseases, Metabolic, Inborn / Q000175:diagnosis* / Q000188:drug therapy / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D015997:Neonatal Screening