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This Article Full Text Full Text (PDF) 076679.Supplemental Data All Versions of this Article: clinchem.2006.076679v1 53/4/717    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Strnadová, K. A. Articles by Bodamer, O. A. Search for Related Content PubMed PubMed Citation Articles by Strnadová, K. A. Articles by Bodamer, O. A. Related Collections Molecular Diagnostics and Genetics General Clinical Chemistry Pediatric Clinical Chemistry Endocrinology and Metabolism Automation and Analytical Techniques

Long-Term Stability of Amino Acids and Acylcarnitines in Dried Blood Spots

¹ Department of Paediatrics, 3rd Faculty of Medicine, Charles University, Prague, Czech Republic.
² Department of General Pediatrics, University Children’s Hospital Vienna, Vienna, Austria.
³ Section of Clinical Biometrics, Core Unit for Medical Statistics and Informatics, Medical, University of Vienna, Vienna, Austria.
⁴ Pharm-analyt Laboratory GmbH, Baden, Germany.
⁵ Children’s Hospital British Columbia University, Vancouver, British Columbia, Canada.

^aAddress correspondence to this author at: Department of General Pediatrics, Division of Biochemical and Pediatric Genetics, University Children’s Hospital Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria. Fax 43-1-406-3484; e-mail olaf.bodamer{at}meduniwien.ac.at.

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.

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