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1.
Clin Chem ; 53(4): 717-22, 2007 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-17272485

RESUMEN

BACKGROUND: Dried blood filter cards, collected for newborn screening, are often stored for long periods of time. They may be suitable for the retrospective diagnosis of inborn errors of metabolism, but no data are currently available on the long-term stability of amino acids and acylcarnitine species. METHODS: We analyzed amino acids and acylcarnitines by tandem mass spectrometry in 660 anonymous, randomly selected filter cards from 1989 through 2004. We assessed long-term stability of metabolites by linear regression and estimated annual decrease of concentration for each metabolite. RESULTS: Concentrations of free carnitine increased by 7.6% per year during the first 5 years of storage and decreased by 1.4% per year thereafter. Alanine, arginine, leucine, methionine, and phenylalanine decreased by 6.5%, 3.3%, 3.1%, 7.3%, and 5.7% per year, respectively. Acetylcarnitine, propionylcarnitine, citrulline, glycine, and ornithine decreased by 18.5%, 27.4%, 8.1%, 14.7%, and 16.3% per year during the first 5 years, respectively; thereafter the decline was more gradual. Tyrosine decreased by 1.7% per year during the first 5 years and 7.9% per year thereafter. We could not analyze medium- and long-chain acylcarnitine species because of low physiological concentrations. CONCLUSIONS: Estimation of the annual decrease of metabolites may allow for the retrospective diagnosis of inborn errors of metabolism in filter cards that have been stored for long periods of time.


Asunto(s)
Aminoácidos/sangre , Recolección de Muestras de Sangre , Carnitina/análogos & derivados , Tamizaje Neonatal/métodos , Carnitina/sangre , Humanos , Recién Nacido , Modelos Lineales , Errores Innatos del Metabolismo/diagnóstico , Modelos Biológicos , Factores de Tiempo
2.
Clin Chim Acta ; 373(1-2): 27-31, 2006 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-16797519

RESUMEN

BACKGROUND: Detection of amino acids (AA), acylcarnitines (AC), and guanidinoacetate (GAA) in dried blood spots by tandem mass spectrometry has made it possible to detect different inborn errors of metabolism in neonatal screening programs. Despite its proven sensitivity many issues related to sample preparation remain unsolved. Hematocrit has a profound effect on blood viscosity, and may thereby influence flux and diffusion properties of the blood. As newborn infants show a considerable interindividual variability of hematocrit levels, we investigated its effect on levels of AA and AC in dried blood spots. METHODS: Blood samples with defined hematocrit levels (20%, 30%, 40%, 50%, 60%) were produced by diluting blood cells with plasma from a single donor. Forty dried blood spots were made for each hematocrit level and a central as well as a peripheral 3 mm disk was punched and analysed for AA, AC, and GAA, respectively. RESULTS: Levels of most AA and GAA increased significantly with increasing hematocrit (p<0.001), while the effect of hematocrit on some AA was less pronounced. Total AC, free carnitine, some long, medium and short chain AC correlated positively with hematocrit levels (p<0.001). In samples with low hematocrit, levels of most AA and free carnitine were higher in the peripheral than in the central disk (p<0.0001). CONCLUSIONS: Both hematocrit and position of the disk within the dried blood spot have a significant and sometimes additive effect on levels of AA, AC and GAA in dried blood spots. Theoretically, diagnoses may be missed depending on hematocrit and position of the disk.


Asunto(s)
Aminoácidos/sangre , Manchas de Sangre , Carnitina/análogos & derivados , Espectrometría de Masas en Tándem/métodos , Aminoácidos/metabolismo , Recolección de Muestras de Sangre , Carnitina/sangre , Glicina/análogos & derivados , Glicina/sangre , Glicina/metabolismo , Hematócrito/métodos , Humanos , Sensibilidad y Especificidad
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