title: Estimation of trueness of measurement results obtained in external quality assessment.
abstract: BACKGROUND
  We demonstrated that lyophilised EQA/PT control materials, under certain circumstances, provide equal information about bias values as pools of native patient sera, and that in some cases, long-term reliable work with such materials is possible.
  
  
  METHODS
  Bias values, estimated from results of routine surveys of EQA SEKK (Czech Republic) programmes for eight basic blood serum analytes using lyophilised control materials, were compared with bias values reached in the CAP (USA) programme where pools of native and lyophilised patient sera were used.
  
  
  RESULTS
  Results for the components Na, K, Mg, Cl, P, urea, glucose, and uric acid were assessed. No significant differences were found between the bias values estimated by CAP using native sera, and those estimated by SEKK using lyophilised sera.
  
  
  CONCLUSIONS
  It can be concluded that well-prepared lyophilised control materials may show the required commutability level. If so, they constitute a practical and cost-efficient alternative to native or fresh frozen sera when assessing bias.
authors.affiliation: Charles University Prague, University Hospital Hradec Kralove, Czech Republic.
authors.forename: Bedrich
authors.initials: B
authors.lastname: Friedecky
authors.forename: Josef
authors.initials: J
authors.lastname: Kratochvila
authors.forename: Marek
authors.initials: M
authors.lastname: Budina
mesh_terms: D015415:Biomarkers / Q000097:blood; D019411:Clinical Laboratory Techniques / Q000379:methods*; D006801:Humans; D011785:Quality Assurance, Health Care / Q000706:statistics & numerical data*; D011786:Quality Control
chemical_list: D015415:Biomarkers