title: Comparative performance of two methods that assess the quality of international normalized ratio measures.
abstract: OBJECTIVE
  Two methods, Petersen's error grid analysis and Shermock's method to detect clinically important differences, were recently developed to advance the assessment of analytic performance of point-of-care INR devices. Both methods predict when alternate INR measures lead to different clinical decisions. Our goal was to compare their performance characteristics.
  
  
  METHODS
  Performance characteristics were assessed by comparing the models' predictions to clinical decisions that were directly measured in a previous experiment.
  
  
  RESULTS
  Shermock's method (82% of predictions correct) demonstrated superior predictive performance compared with the error grid analysis (75% of predictions correct, p=0.008). Shermock's method was particularly superior at identifying the clinical decisions that actually disagreed (79% for Shermock's method vs. 47% for error grid). Consequently, Shermock's method was superior at identifying a POC device with poor performance (79% accuracy vs. 70%, p=0.006).
  
  
  CONCLUSIONS
  Shermock's method had superior performance characteristics and should be integrated into analytic strategies to assess POC INR devices.
authors.affiliation: Center for Pharmaceutical Outcomes, The Johns Hopkins Medical Institutions, Baltimore, MD 21287, USA. kenneth@jhmi.edu
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Shermock
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Tandon
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Sorgen
authors.forename: Danielle C
authors.initials: DC
authors.lastname: Lavallee
authors.forename: William
authors.initials: W
authors.lastname: Clarke
authors.forename: Michael B
authors.initials: MB
authors.lastname: Streiff
mesh_terms: D002623:Chemistry Techniques, Analytical / Q000379:methods / Q000592:standards*; D003661:Decision Support Techniques; D006801:Humans; D019934:International Normalized Ratio / Q000379:methods* / Q000592:standards; D019095:Point-of-Care Systems / Q000592:standards*; D011237:Predictive Value of Tests; D011786:Quality Control; D011933:Reagent Kits, Diagnostic; D012015:Reference Standards; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013925:Thromboplastin / Q000737:chemistry; D014859:Warfarin / Q000008:administration & dosage
chemical_list: D011933:Reagent Kits, Diagnostic; D014859:Warfarin; D013925:Thromboplastin