[Expanded newborn screening in the Region of Murcia, Spain. Three-years experience.]
Sección de Metabolopatías, Centro de Bioquímica y Genética Clínica, Hospital Universitario Virgen de la Arrixaca, Murcia, España.Medicina Clínica (Impact Factor: 1.42). 12/2011;
BACKGROUND AND OBJECTIVE: 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. PATIENTS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.
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ABSTRACT: Unlabelled: Quantification of acylcarnitines is used for screening and diagnosis of inborn error of metabolism (IEM). While newborn screening is performed in dried blood spots (DBSs), general metabolic investigation is often performed in plasma. Information on the correlation between plasma and DBS acylcarnitine profiles is scarce. In this study, we directly compared acylcarnitine concentrations measured in DBS with those in the corresponding plasma sample. Additionally, we tested whether ratios of acylcarnitines in both matrices are helpful for diagnostic purpose when primary markers fail. Study design: DBS and plasma were obtained from controls and patients with a known IEM. (Acyl)carnitines were converted to their corresponding butyl esters and analyzed using HPLC/MS/MS. Results: Free carnitine concentrations were 36% higher in plasma compared to DBS. In contrast, in patients with carnitine palmitoyltransferase 1 (CPT-1) deficiency free carnitine concentration in DBS was 4 times the concentration measured in plasma. In carnitine palmitoyltransferase 2 (CPT-2) deficiency, primary diagnostic markers were abnormal in plasma but could also be normal in DBS. The calculated ratios for CPT-1 (C0/(C16+C18)) and CPT-2 ((C16+C18:1)/C2) revealed abnormal values in plasma. However, normal ratios were found in DBS of two (out of five) samples obtained from patients diagnosed with CPT-2. Conclusions: Relying on primary acylcarnitine markers, CPT-1 deficiency can be missed when analysis is performed in plasma, whereas CPT-2 deficiency can be missed when analysis is performed in DBS. Ratios of the primary markers to other acylcarnitines restore diagnostic recognition completely for CPT-1 and CPT-2 in plasma, while CPT-2 can still be missed in DBS.
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