Received on October 1, 2004
Accepted on February 1, 2005

Laboratory Management

Age-Related Variations in Acylcarnitine and Free Carnitine Concentrations Measured by Tandem Mass Spectrometry

¹ Newborn Screening Center, Laboratory of Pediatrics, Free University of Brussels, Brussels, Belgium
² Scientific Institute for Public Health (IPH), Epidemiology Unit, Brussels, Belgium
³ Department of Pediatrics, Queen Fabiola University Children's Hospital, Free University of Brussels, Brussels, Belgium
⁴ Newborn Screening Center, Laboratory of Pediatrics, Free University of Brussels, Brussels, Belgium, and Department of Pediatrics, Queen Fabiola University Children's Hospital, Free University of Brussels, Brussels, Belgium

^* To whom correspondence should be addressed. E-mail: catia.cavedon{at}gmail.com.

Background: The acylcarnitine profiles obtained from dried blood spots on "Guthrie cards" have been widely used for the diagnosis and follow-up of children suspected of carrying an inherited error of metabolism, but little attention has been paid to potential age-related variation in the reference values. In this study, we evaluated the variations in free carnitine and acylcarnitine concentrations with age, as measured by tandem mass spectrometry.

Methods: Filter-paper blood spots were collected from 433 healthy individuals over a period of 17 months. Eight age groups were defined: cord blood, 3-6 days (control group), 15-55 days, 2-18 months, 19-59 months, 5-10 years, 11-17 years, and 18-54 years. Free carnitine and acylcarnitines were measured for each individual. Mean values were calculated for each age group and compared with those for the control group.

Results: Free carnitine was significantly higher in older children than in newborns (P <0.05), but the concentrations of several acylcarnitines tended to be significantly lower on cord blood and in groups of older children than in the control group. Only minor sex-related differences were observed.

Conclusion: Although the risk of underdiagnosis of fatty acid oxidation disorders with the use of newborn values as reference can be considered as small, in some circumstances the use of age-related reference values may have a potential impact on the diagnosis and management of inherited errors of metabolism.