title: From radioimmunoassay to mass spectrometry: a new method to quantify orexin-A (hypocretin-1) in cerebrospinal fluid.
abstract: I(125) radioimmunoassay (RIA) is currently the standard technique for quantifying cerebrospinal fluid (CSF) orexin-A/hypocretin-1, a biomarker used to diagnose narcolepsy type 1. However, orexin-A RIA is liable to undergo cross-reactions with matrix constituents generating interference, high variability between batches, low precision and accuracy, and requires special radioactivity precautions. Here we developed the first quantitative mass spectrometry assay of orexin-A based on a multiple reaction monitoring (MRM) approach. This method was tested in keeping with the Clinical and Laboratory Standards Institute (CLSI) guidelines and its clinical relevance was confirmed by comparing patients with narcolepsy type 1 versus patients with other neurological conditions. The results obtained using MRM and RIA methods were highly correlated, and Bland-Altman analysis established their interchangeability. However, the MRM values had a wider distribution and were 2.5 time lower than the RIA findings. In conclusion, this method of assay provides a useful alternative to RIA to quantify orexin-A, and may well replace it not only in narcolepsy type 1, but also in the increasing number of pathologies in which the quantification of this analyte is relevant.
authors.affiliation: CHU Montpellier, Institut de Recherche en Biothérapie, hôpital St Eloi, Laboratoire de Biochimie Protéomique Clinique et CRB, Montpellier, F-34000 France.|Université de Montpellier, Montpellier, F-34000 France. INSERM U1183, Montpellier, F-34000 France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Hirtz
authors.affiliation: CHU Montpellier, Institut de Recherche en Biothérapie, hôpital St Eloi, Laboratoire de Biochimie Protéomique Clinique et CRB, Montpellier, F-34000 France.|Université de Montpellier, Montpellier, F-34000 France. INSERM U1183, Montpellier, F-34000 France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Vialaret
authors.affiliation: CHU Montpellier, Institut de Recherche en Biothérapie, hôpital St Eloi, Laboratoire de Biochimie Protéomique Clinique et CRB, Montpellier, F-34000 France.|Université de Montpellier, Montpellier, F-34000 France. INSERM U1183, Montpellier, F-34000 France.|Memory Research Resources center, Department of Neurology, Gui-de-Chauliac Hospital, Montpellier University Hospital, F-34000 France.
authors.forename: Audrey
authors.initials: A
authors.lastname: Gabelle
authors.affiliation: CHU Montpellier, Institut de Recherche en Biothérapie, hôpital St Eloi, Laboratoire de Biochimie Protéomique Clinique et CRB, Montpellier, F-34000 France.|Université de Montpellier, Montpellier, F-34000 France. INSERM U1183, Montpellier, F-34000 France.
authors.forename: Nora
authors.initials: N
authors.lastname: Nowak
authors.affiliation: National Reference Centre for Orphan Diseases, Narcolepsy, Idiopathic hypersomnia and Kleine-Levin Syndrome, France.|Sleep Disorders Center, Department of Neurology, Gui-de-Chauliac Hospital, CHU Montpellier, Inserm U1061, Montpellier, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Dauvilliers
authors.affiliation: CHU Montpellier, Institut de Recherche en Biothérapie, hôpital St Eloi, Laboratoire de Biochimie Protéomique Clinique et CRB, Montpellier, F-34000 France.|Université de Montpellier, Montpellier, F-34000 France. INSERM U1183, Montpellier, F-34000 France.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Lehmann
mesh_terms: D000293:Adolescent; D000328:Adult; D002555:Cerebrospinal Fluid / Q000737:chemistry*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D013058:Mass Spectrometry / Q000379:methods*; D008875:Middle Aged; D009290:Narcolepsy / Q000175:diagnosis*; D000068797:Orexins / Q000134:cerebrospinal fluid*; D011863:Radioimmunoassay / Q000379:methods*; D055815:Young Adult
chemical_list: D000068797:Orexins