title: Is calibration the cause of variation in liquid chromatography tandem mass spectrometry testosterone measurement?
abstract: BACKGROUND
  Testosterone measurement by liquid chromatography tandem mass spectrometry (LC-MS/MS) is well accepted as the preferred technique for the analysis of testosterone. Variation is seen between assays and this may be due to differences in calibration as commercial calibrators for this assay are not readily available. We investigated the effects calibration in routine clinical LC-MS/MS assays.
  
  
  METHODS
  All LC-MS/MS users that were registered with the UKNEQAS external quality assurance scheme for testosterone were invited to take part in the study. A set of seven serum samples and serum-based calibrators were sent to all laboratories that expressed an interest. The laboratories were instructed to analyse all samples using there own calibrators and return the results and a method questionnaire for analysis.
  
  
  RESULTS
  Fifteen laboratories took part in the study. There was no consensus on supplier of testosterone or matrix for the preparation of calibrators and all were prepared in-house. Also, a wide variety of mass spectrometers, internal standards, chromatography conditions and sample extractions were used. The variation in results did not improve when the results were corrected with a common calibrator.
  
  
  CONCLUSIONS
  The variation in results obtained could not be attributed to variations in calibrators. The differences in methodologies between laboratories must be the reason for this variation.
authors.affiliation: The University of Manchester, Manchester Academic Health Science Centre, Manchester, UK. Laura.owen@uhsm.nhs.uk
authors.forename: L J
authors.initials: LJ
authors.lastname: Owen
authors.forename: P R
authors.initials: PR
authors.lastname: MacDonald
authors.forename: B G
authors.initials: BG
authors.lastname: Keevil
mesh_terms: D002138:Calibration; D002853:Chromatography, Liquid / Q000379:methods / Q000592:standards; D005260:Female; D006801:Humans; D008297:Male; D053719:Tandem Mass Spectrometry / Q000379:methods* / Q000592:standards*; D013739:Testosterone / Q000097:blood*
chemical_list: D013739:Testosterone
keywords: Mass spectrometry; analytes; laboratory methods; steroid hormones