title: A superior method to report clinically relevant quality information about the point-of-care INR device performance compared with the International Organization for Standardization guidelines.
abstract: BACKGROUND
  A revised ISO guideline was recently published that recommended methods to assess the quality of point-of-care INR measures. We assessed the relative performance of the ISO methods and a method that we developed.
  
  
  METHODS
  We compared the ability of the ISO and the Shermock methods to predict when the INR measures lead to identical or different clinical decisions. Clinical decisions that were directly measured in a previous trial were used as a standard.
  
  
  RESULTS
  The Shermock method was significantly better (82% of predictions correct) than the revised ISO method (61% correct, p<0.0001) at predicting when two INR measures lead to identical or different clinical decisions. Only 41% of decisions predicted to disagree by the revised ISO method actually disagreed; while only 51% of decisions that actually agreed were correctly predicted.
  
  
  CONCLUSIONS
  The Shermock method is superior in providing information that clinicians and patients care most about regarding the quality of the INR measures used to guide clinical decisions. Regulatory agencies should strongly consider incorporating the Shermock method into the device approval process. Local clinical laboratories should consider using the Shermock method in quality assurance assessments.
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: William
authors.initials: W
authors.lastname: Clarke
authors.forename: Michael B
authors.initials: MB
authors.lastname: Streiff
mesh_terms: D005069:Evaluation Studies as Topic; D017408:Guidelines as Topic / Q000592:standards*; D006801:Humans; D019934:International Normalized Ratio / Q000592:standards*; D008722:Methods; D019095:Point-of-Care Systems / Q000592:standards*; D011786:Quality Control; D012015:Reference Standards