title: Performance of a point-of-care device in determining prothrombin time in supra-therapeutic INRs.
abstract: BACKGROUND
  Point-of-care (POC) devices have been widely adopted for monitoring prothrombin time (PT) (INR) following the demonstration of their accuracy compared to standard INR determination. However, guidelines suggest confirmation of POC results when INRs increase above therapeutic range, due to concerns regarding possible inferior performance of POC devices in high INR levels. Unfortunately, patients with supra-therapeutic INRs are underrepresented in studies that validated these devices.
  
  
  METHODS
  We performed a prospective evaluation of the performance of a POC device in monitoring oral anticoagulation in patients with INR values above 3.5 in a University outpatient anticoagulation clinic. During a 6-month period, 2322 INR determinations were performed with a POC device, and results above 3.5 were immediately repeated on an automated coagulometer.
  
  
  RESULTS
  Dual INR determinations by two methods were obtained in 160 visits, with a mean INR from the POC device of 4.52 ± 0.96. Both classical statistics and clinical concordance analysis yielded satisfactory results when the two methods were compared.
  
  
  CONCLUSIONS
  Our results demonstrate that POC devices present good correlation with standard laboratory methods for PT determination in supra-therapeutic INRs and that differences in clinical management do not support the need for systematic confirmation of these results in nonbleeding patients.
authors.affiliation: Hematology and Hemotherapy Center, University of Campinas, Campinas, SP, Brazil.
authors.forename: V A M
authors.initials: VA
authors.lastname: Hashimoto
authors.forename: E V
authors.initials: EV
authors.lastname: De Paula
authors.forename: M P
authors.initials: MP
authors.lastname: Colella
authors.forename: M M
authors.initials: MM
authors.lastname: Luz Fiusa
authors.forename: S A L
authors.initials: SA
authors.lastname: Montalvao
authors.forename: T F G S
authors.initials: TF
authors.lastname: Machado
authors.forename: F A
authors.initials: FA
authors.lastname: Orsi
authors.forename: J M
authors.initials: JM
authors.lastname: Annichino-Bizzacchi
mesh_terms: D006801:Humans; D019934:International Normalized Ratio / Q000295:instrumentation / Q000592:standards; D019095:Point-of-Care Systems / Q000592:standards*; D011517:Prothrombin Time / Q000295:instrumentation* / Q000592:standards*