title: Surprising causes of C5-carnitine false positive results in newborn screening.
abstract: During an 18-month period, we noticed an alarming increase of newborn screening false positivity rate in identifying isovaleric acidemia. In 50 of 50 newborns presenting elevated C5-carnitine, we confirmed the presence of pivaloylcarnitine. Exogenous pivalate administration had been previously identified as the causal agent of this concern. No pivalic-ester prodrug is commercially available in Belgium, but pivalic derivates are also used in the cosmetic industry as emollient under the term "neopentanoate". We have identified neopentanoate-esters in a nipple-fissure unguent that was provided to young mothers. Ceasing distribution of this product hugely reduced the C5-carnitine false positivity rate.
authors.affiliation: Biochemical Genetics Laboratory, Human Genetics, CHU Liege, University of Liege, Belgium. Electronic address: F.Boemer@chu.ulg.ac.be.
authors.forename: François
authors.initials: F
authors.lastname: Boemer
authors.affiliation: Biochemical Genetics Laboratory, Human Genetics, CHU Liege, University of Liege, Belgium.
authors.forename: Roland
authors.initials: R
authors.lastname: Schoos
authors.affiliation: Neonatal Intensive Care Unit, University of Liege, Centre Hospitalier Régional de la Citadelle, Liege, Belgium.
authors.forename: Virginie
authors.initials: V
authors.lastname: de Halleux
authors.affiliation: Neonatal Intensive Care Unit, University of Liege, Centre Hospitalier Régional de la Citadelle, Liege, Belgium.
authors.forename: Masendu
authors.initials: M
authors.lastname: Kalenga
authors.affiliation: Metabolic Unit, Human Genetics, CHU Liege, University of Liege, Belgium.
authors.forename: François-Guillaume
authors.initials: FG
authors.lastname: Debray
mesh_terms: D000592:Amino Acid Metabolism, Inborn Errors / Q000175:diagnosis* / Q000378:metabolism; D001530:Belgium; D002331:Carnitine / Q000031:analogs & derivatives / Q000097:blood*; D005189:False Positive Reactions; D006801:Humans; D007231:Infant, Newborn; D050769:Isovaleryl-CoA Dehydrogenase / Q000172:deficiency* / Q000378:metabolism; D013058:Mass Spectrometry; D015997:Neonatal Screening; D009824:Ointments; D010421:Pentanoic Acids / Q000008:administration & dosage; D011355:Prodrugs / Q000494:pharmacology*; D012307:Risk Factors
chemical_list: D009824:Ointments; D010421:Pentanoic Acids; D011355:Prodrugs; C005566:pivalic acid; C054040:pivaloylcarnitine; D050769:Isovaleryl-CoA Dehydrogenase; D002331:Carnitine
keywords: C5-carnitine; False positive; Inborn error of metabolism; Mass spectrometry; Newborn screening; Pivalic acid