title: Determination of homocitrulline in urine of patients with HHH syndrome by liquid chromatography tandem mass spectrometry.
abstract: A liquid chromatography tandem mass spectrometric method is described for the analysis of homocitrulline in human urine, a key metabolite in the differential diagnosis of hyperammonemia, hyperornithinemia, homocitrullinuria (HHH) syndrome. Urine samples were prepared by mere five-fold dilution with a mixture of internal standards (2H2-citrulline and 2H3-creatinine) used for the simultaneous quantification of creatinine. Analytes were separated on a cyano column and eluted isocratically within seven min. Detection was achieved by monitoring transitions of 190 > 84 and 190 > 127 for homocitrulline, 178 > 115 for 2H2-citrulline, 114 > 44 for creatinine and 117 > 47 for 2H3-creatinine. Calibration curves were linear up to 100 micromol/L. Intraday (n = 7) and interday (n = 6) variations were less than 10%. In urine samples from three siblings confirmed to have HHH syndrome, homocitrulline levels were at 13.3 (74), 21.1 (50) and 108.2 (103) mmol/mol creatinine (micromol/L). Control values were 0-9 mmol/mol creatinine (n = 120). The current method solves specificity issues in homocitrulline determination often encountered with some ninhydrin-based systems (coelution with methionine) and some o-phthalaldehyde-based ones (coelution with taurine), and presents an attractive alternative with a relatively high throughput.
authors.affiliation: National Laboratory for Newborn Screening, King Faisal Specialist Hospital and Research Center, P.O. Box 3354, Riyadh 11211, Saudi Arabia.
authors.forename: Osama Y
authors.initials: OY
authors.lastname: Al-Dirbashi
authors.forename: Zuhair N
authors.initials: ZN
authors.lastname: Al-Hassnan
authors.forename: Mohamed S
authors.initials: MS
authors.lastname: Rashed
mesh_terms: D000641:Ammonia / Q000378:metabolism*; D002853:Chromatography, Liquid / Q000379:methods*; D002956:Citrulline / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000652:urine; D003404:Creatinine / Q000378:metabolism; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*; D009952:Ornithine / Q000378:metabolism*; D013577:Syndrome
chemical_list: C001352:homocitrulline; D002956:Citrulline; D000641:Ammonia; D003404:Creatinine; D009952:Ornithine