title: Age related reference values for urine creatine and guanidinoacetic acid concentration in children and adolescents by gas chromatography-mass spectrometry.
abstract: A new gas chromatography-mass spectrometry method for routine quantification of urine creatine and guanidinoacetic acid (GAA) has been developed to provide a fast, reliable and inexpensive metabolic screening. Our method uses a two-step derivatization procedure which involves a reaction with hexafluoroacetylacetone followed by a reaction with mono-trimethylsilyltrifluoroacetamide. The standard curves showed linearity over a range of 43-4269 micromol/l for GAA and 38-7325 micromol/l for creatine, which covers the range of GAA and creatine normally found in urine. The lower detection limit is 1.54 micromol/l for GAA and 1.22 micromol/l for creatine, whereas the lower quantification limit is 5.04 micromol/l for GAA and 4.19 micromol/l for creatine. This method was also employed to establish reference values for GAA and creatine in healthy infants, children and adolescents based on the analysis of 169 urine samples. Although no sex differences were observed, normal GAA urinary levels and creatine excretion are distinct in age-related subgroups. We identified a statistically significant age difference in two major groups for GAA (children under 4 years, 18-159 micromol/mmol creatinine; and subjects of 5-16 years, 18-130 micromol/mmol creatinine) whereas three groups were discriminated for creatine (children under 4 years, 0.04-1.51 mmol/mmol creatinine; subjects of 5-11 years, 0.04-1.07 mmol/mmol creatinine; and subjects of 12-16 years, 0.04-0.56 mmol/mmol creatinine).
authors.affiliation: Unidade de Biologia Clínica, do Instituto de Genética Médica Jacinto de Magalhães, Praça Pedro Nunes, 88-4099-028, Oporto, Portugal.
authors.forename: Carla
authors.initials: C
authors.lastname: Valongo
authors.forename: Maria Luís
authors.initials: ML
authors.lastname: Cardoso
authors.forename: Pedro
authors.initials: P
authors.lastname: Domingues
authors.forename: Lígia
authors.initials: L
authors.lastname: Almeida
authors.forename: Nanda
authors.initials: N
authors.lastname: Verhoeven
authors.forename: Gajja
authors.initials: G
authors.lastname: Salomons
authors.forename: Cornelis
authors.initials: C
authors.lastname: Jakobs
authors.forename: Laura
authors.initials: L
authors.lastname: Vilarinho
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D003401:Creatine / Q000172:deficiency / Q000652:urine*; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D005998:Glycine / Q000031:analogs & derivatives* / Q000652:urine*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D012016:Reference Values; D012737:Sex Factors
chemical_list: C004946:glycocyamine; D003401:Creatine; D005998:Glycine