title: INR comparison between the CoaguChek S and a standard laboratory method among patients with self-management of oral anticoagulation.
abstract: BACKGROUND
  Portable coagulation monitors have been developed to measure International Normalised Ratio (INR) in orally anticoagulated patients using capillary whole blood from a finger stick. Because of unsatisfactory precision of some of the monitors in comparison with laboratory methods new devices are being developed. In the present study we compared INR determination with the CoaguChek S device with a standard laboratory method among patients with self-management of oral anticoagulation (OAC).
  
  
  METHODS
  Two hundred and forty-two patients performing self-management of OAC were enrolled into this study. Parallel INR measurements were performed within one hour. Capillary INR measurements (INRcap) were done by the patients with the CoaguChek S and venous INR (INRven) by qualified medical staff using a standard laboratory method.
  
  
  RESULTS
  We found a correlation coefficient (r(S)) of 0.85 (95% CI: 0.81-0.88) among the 242 patients between INRven and INRcap. In 84.4% of the INR parallel measurements the difference between the two values was below 0.5 INR units. In only 2 of 242 cases the difference was >1 INR unit (1.1 and 1.3). The slope of the Passing Bablok regression line was 0.91 (95% CI: 0.83-1.0) and the y-intercept 0.06 (95% CI: -0.20-0.25). Agreement between both methods was 90.5% (95% CI: 86.8-94.2) and standard-agreement even 97.1% (95% CI: 95-99.2).
  
  
  CONCLUSIONS
  INR measurement with CoaguChek S device by trained patients revealed reliable results in comparison to the values obtained with a standard laboratory method.
authors.affiliation: Division of Hematology and Central Hematology Laboratory, Kantonsspital, Lucerne, 6000 Lucerne 16, Switzerland.
authors.forename: Dorota Palka
authors.initials: DP
authors.lastname: Hentrich
authors.forename: Jordan
authors.initials: J
authors.lastname: Fritschi
authors.forename: Pascale Raddatz
authors.initials: PR
authors.lastname: Müller
authors.forename: Walter A
authors.initials: WA
authors.lastname: Wuillemin
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage*; D019411:Clinical Laboratory Techniques; D003374:Coumarins / Q000008:administration & dosage; D016903:Drug Monitoring / Q000295:instrumentation*; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D011517:Prothrombin Time; D012189:Retrospective Studies; D013927:Thrombosis / Q000188:drug therapy
chemical_list: D000925:Anticoagulants; D003374:Coumarins; C030123:coumarin