title: Evaluation of commercial assays for vancomycin and aminoglycosides in serum: a comparison of accuracy and precision based on external quality assessment.
abstract: OBJECTIVE
  To compare the accuracy and precision of commercial assay techniques in the measurement of gentamicin, tobramycin, amikacin, netilmicin and vancomycin in serum.
  
  
  METHODS
  Data from the measurement of 40 external quality assessment samples from 358 laboratories providing a therapeutic drug monitoring service were analysed.
  
  
  RESULTS
  Significant differences between techniques in accuracy and precision were observed for all drugs. Coefficients of variation ranged from 4.1% to 9.8% for the aminoglycosides and from 6.7% to 11.7% for vancomycin. The percentage difference in measurements from the weighed-in drug concentration ranged from -10.1% to +4.0% for the aminoglycosides and from -3.5% to +5.7% for vancomycin. The Dade Behring Emit immunoassay was notable in producing significantly more outliers (>4 S.D. from the weighed-in concentration) than other techniques in the measurement of gentamicin, amikacin and vancomycin.
  
  
  CONCLUSIONS
  All assays performed to a satisfactory standard for measurement in non-renal patients, but none met the more stringent standards desirable for monitoring patients with renal impairment.
authors.affiliation: Department of Pharmacology, Therapeutics & Toxicology, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN, UK. wilsonjf@cardiff.ac.uk
authors.forename: John F
authors.initials: JF
authors.lastname: Wilson
authors.forename: Alan C
authors.initials: AC
authors.lastname: Davis
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Tobin
mesh_terms: D000900:Anti-Bacterial Agents / Q000097:blood*; D006801:Humans; D011786:Quality Control; D011933:Reagent Kits, Diagnostic; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014640:Vancomycin / Q000097:blood*
chemical_list: D000900:Anti-Bacterial Agents; D011933:Reagent Kits, Diagnostic; D014640:Vancomycin