title: Neonatal blood carnitine concentrations: normative data by electrospray tandem mass spectometry.
abstract: Despite a number of published reports, there is limited information about carnitine metabolism in the newborn. To establish normative data, we analyzed whole-blood carnitine concentrations in 24,644 newborns at age 1.85 +/- 0.95 d and umbilical cord whole blood and plasma carnitine concentrations in 50 full-term newborns. Total carnitine (TC), free carnitine (FC), and acylcarnitine (AC) were measured by electrospray tandem mass spectrometry. AC/FC ratios were derived from these measurements. The entire cohort was stratified according to TC values into a middle TC group representing 90% of the population and lower and upper TC groups representing 5% of the population, respectively. Normative data were derived from the middle TC group of full-term infants (N = 19,595). TC was 72.42 +/- 20.75 microM, FC was 44.94 +/- 14.99 microM, AC was 27.48 +/- 8.05 microM, and AC/FC ratio was 0.64 +/- 0.19 (+/-SD). These values differed significantly from umbilical cord whole blood TC values of 31.27 +/- 10.54 microM determined in 50 samples. No meaningful correlation was found between TC and gestational age or birth weight in any group. In controlled analyses, prematurity was not associated with TC levels, whereas low birth weight (<2500 g) and male sex were significantly associated with higher TC levels. The association of low birth weight with higher TC values may be related to decreased tissue carnitine uptake. The sex effect may be related to hormonal influences on carnitine metabolism. Our study provides normative data of carnitine values measured by the highly precise method of electrospray tandem mass spectrometry in a large cohort of newborns and provides the basis for future studies of carnitine metabolism in health and disease states during the neonatal period.
authors.affiliation: Neo Gen Screening, Division of BioAnalytical Chemistry and Mass Spectrometry, Bridgeville, PA 15017, USA. dcd1@columbia.edu
authors.forename: Donald H
authors.initials: DH
authors.lastname: Chace
authors.forename: Roser
authors.initials: R
authors.lastname: Pons
authors.forename: Claudia A
authors.initials: CA
authors.lastname: Chiriboga
authors.forename: Donald J
authors.initials: DJ
authors.lastname: McMahon
authors.forename: Ingrid
authors.initials: I
authors.lastname: Tein
authors.forename: Edwin W
authors.initials: EW
authors.lastname: Naylor
authors.forename: Darryl C
authors.initials: DC
authors.lastname: De Vivo
mesh_terms: D002331:Carnitine / Q000032:analysis* / Q000097:blood*; D002624:Chemistry, Clinical / Q000592:standards*; D005260:Female; D005312:Fetal Blood; D006706:Homeostasis; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D015999:Multivariate Analysis; D012016:Reference Values; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002331:Carnitine