title: Comparative analysis of serotonin in equine plasma with liquid chromatography--tandem mass spectrometry and enzyme-linked immunosorbent assay.
abstract: Serotonin is regularly measured in equine platelet-poor plasma in research settings. However, reported reference values vary between studies, partially because plasma serotonin concentrations are very low and a reliable and affordable detection method is lacking. A simple, rapid, and sensitive method for serotonin determination in equine platelet-poor plasma using liquid chromatography--tandem mass spectrometry (LC-MS/MS) was developed and validated. Results of a commercially available enzyme-linked immunosorbent assay (ELISA) were compared to the LC-MS/MS results, in order to validate a test more suitable for use in a clinical situation. For LC-MS/MS, 500 µl of plasma was required, and deuterated serotonin was used as an internal standard. The sample preparation was based upon a simple liquid extraction into ethyl acetate. Chromatographic separation was performed with an acetic acid--acetonitrile mobile phase gradient elution. Linearity was demonstrated between 3 ng/ml and 100 ng/ml. A limit of quantification of 3 ng/ml was achieved, corresponding to a limit of detection of 0.10 ng/ml. Comparison of LC-MS/MS and ELISA with Passing-Bablok regression and Bland--Altman plotting showed a poor agreement between the 2 methods, with an increasing difference within the higher range of measurements. Caution is needed when extrapolating results from sources using different analytical techniques.
authors.affiliation: Department of Large Animal Internal Medicine and Clinical Biology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium. sara.torfs@ugent.be
authors.forename: Sara C
authors.initials: SC
authors.lastname: Torfs
authors.forename: An A
authors.initials: AA
authors.lastname: Maes
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Delesalle
authors.forename: Piet
authors.initials: P
authors.lastname: Deprez
authors.forename: Siska M
authors.initials: SM
authors.lastname: Croubels
mesh_terms: D000818:Animals; D002853:Chromatography, Liquid / Q000379:methods / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary*; D006736:Horses / Q000097:blood*; D015394:Molecular Structure; D012701:Serotonin / Q000097:blood* / Q000737:chemistry; D053719:Tandem Mass Spectrometry / Q000379:methods / Q000662:veterinary*
chemical_list: D012701:Serotonin