title: Novel LC-MS/MS method for plasma vancomycin: comparison with immunoassays and clinical impact.
abstract: BACKGROUND
  Accurate quantification of vancomycin in plasma is important for adequate dose-adjustment. As literature suggests between-method differences, our first objective was to develop a novel liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for total vancomycin in human plasma and to compare frequently used immunoassays with this method. Secondly, we investigated the clinical impact of between-method quantification differences.
  
  
  METHODS
  For LC-MS/MS, lithium heparin plasma was extracted by adding a precipitation reagent containing the internal standard (vancomycin-des-leucine). Analysis was performed on an Acquity TQD mass spectrometer equipped with an Acquity UPLC 2795 separations module. Our method was analytically validated and compared with four frequently used immunoassays from four different manufacturers. Vancomycin concentrations were clinically classified as toxic, therapeutic and sub-therapeutic. Clinical discordance was calculated using LC-MS/MS as a reference.
  
  
  RESULTS
  A novel LC-MS/MS method using protein precipitation as sole pretreatment and an analysis time of 5.0 min was developed. The assay had a total imprecision of 2.6-8.5%, a limit of quantification of 0.3 mg/L and an accuracy ranging from 101.4 to 111.2%. Using LC-MS/MS as reference, three immunoassays showed a mean proportional difference within 10% and one showed a substantial mean proportional difference of >20%. Clinical discordant interpretation of the obtained concentrations ranged from 6.1 to 22.2%.
  
  
  CONCLUSIONS
  We developed a novel LC-MS/MS method for rapid analysis of total vancomycin concentrations in human plasma. Correlation of the method with immunoassays showed a mean proportional difference >20% for one of the assays, causing discordant clinical interpretation in more than 1 out of 5 samples.
authors.affiliation: University Hospitals Leuven, Department of Laboratory Medicine, B-3000 Leuven, Belgium. Electronic address: matthijsoyaert@telenet.be.
authors.forename: Matthijs
authors.initials: M
authors.lastname: Oyaert
authors.affiliation: University Hospitals Leuven, Department of Laboratory Medicine, B-3000 Leuven, Belgium.
authors.forename: Nele
authors.initials: N
authors.lastname: Peersman
authors.affiliation: University Hospitals Leuven, Department of Laboratory Medicine, B-3000 Leuven, Belgium; KU Leuven - University of Leuven, Department of Microbiology and Immunology, B-3000 Leuven, Belgium.
authors.forename: Davy
authors.initials: D
authors.lastname: Kieffer
authors.affiliation: Antwerp University Hospital, Department of Laboratory Medicine, B-2650 Edegem, Belgium.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Deiteren
authors.affiliation: KU Leuven - University of Leuven, Department of Development and Regeneration, B-3000 Leuven, Belgium; University Hospitals Leuven, Neonatal Intensive Care Unit, B-3000 Leuven, Belgium.
authors.forename: Anne
authors.initials: A
authors.lastname: Smits
authors.affiliation: KU Leuven - University of Leuven, Department of Development and Regeneration, B-3000 Leuven, Belgium; University Hospitals Leuven, Neonatal Intensive Care Unit, B-3000 Leuven, Belgium.
authors.forename: Karel
authors.initials: K
authors.lastname: Allegaert
authors.affiliation: KU Leuven - University of Leuven, Department of Clinical Pharmacology and Pharmacotherapy, B-3000 Leuven, Belgium; University Hospitals Leuven, Pharmacy Department, B-3000 Leuven, Belgium.
authors.forename: Isabel
authors.initials: I
authors.lastname: Spriet
authors.affiliation: University Hospitals Leuven, Department of Laboratory Medicine, B-3000 Leuven, Belgium; KU Leuven - University of Leuven, Department of Microbiology and Immunology, B-3000 Leuven, Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Van Eldere
authors.affiliation: University Hospitals Leuven, Department of Laboratory Medicine, B-3000 Leuven, Belgium; KU Leuven - University of Leuven, Department of Microbiology and Immunology, B-3000 Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Verhaegen
authors.affiliation: University Hospitals Leuven, Department of Laboratory Medicine, B-3000 Leuven, Belgium; KU Leuven - University of Leuven, Department of Cardiovascular Sciences, B-3000 Leuven, Belgium.
authors.forename: Pieter
authors.initials: P
authors.lastname: Vermeersch
authors.affiliation: University Hospitals Leuven, Department of Laboratory Medicine, B-3000 Leuven, Belgium; KU Leuven - University of Leuven, Department of Cardiovascular Sciences, B-3000 Leuven, Belgium.
authors.forename: Steven
authors.initials: S
authors.lastname: Pauwels
mesh_terms: D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D006801:Humans; D007118:Immunoassay; D053719:Tandem Mass Spectrometry / Q000379:methods*; D014640:Vancomycin / Q000097:blood*
chemical_list: D014640:Vancomycin
keywords: LC–MS/MS; Tandem mass spectrometry; Therapeutic drug monitoring; Vancomycin