title: The international normalized ratio according to Owren in liver disease: interlaboratory assessment and determination of international sensitivity index.
abstract: BACKGROUND
  The international normalized ratio (INR) is used to prioritize liver disease patients for transplantation. Previous studies have shown high interlaboratory variability in Quick-based INR determinations in samples of patients with liver disease. We assessed Owren-based INR reagents for analyzing INR in patients with liver disease. Further, we determined the difference between international sensitivity index (ISI) for patients on vitamin K antagonists (ISIVKA) and ISI for patients with liver disease (ISIliver).
  
  
  METHODS
  Twenty patients with liver disease were included, 10 with INR 1.8-3.6 (group A1) and 10 with INR 1.2-1.5 (group C1). Plasma from these patients was analyzed for Owren-based INR in eight Swedish laboratories using either of following reagents: SPA+, Owrens PT or Nycotest PT. To determine ISI liver, the reference thromboplastin RBT/05 and additional 41 patients with liver disease and 20 normal controls were included. ISIVKA was determined according to the WHO procedure. The difference between the ISIVKA and ISIliver was calculated.
  
  
  RESULTS
  The coefficients of variance for the Owren based INR methods were 6.2% in group A1, 3.9 % in group C1 and 5.3% for all patients. The difference between ISIVKA and ISIliver were -0.4%, -0.7% and -0.2% for SPA+, Owrens PT and Nycotest PT respectively.
  
  
  CONCLUSIONS
  Interlaboratory variation in INR analyses according to Owren in patients with liver disease is low and the difference between ISIVKA and ISIliver is below 10% with this method. ISIVKA can therefore be used in the INR calibration, for the Owren reagents studied, when analyzing plasma from patients with liver disease.
authors.affiliation: CLINTEC, Karolinska Institutet, Division of Pediatrics, Astrid Lindgren Children's Hospital, Karolinska University Hospital, Stockholm, Sweden. Electronic address: maria.magnusson@ki.se.
authors.forename: Maria
authors.initials: M
authors.lastname: Magnusson
authors.forename: Margareta
authors.initials: M
authors.lastname: Sten-Linder
authors.forename: Annika
authors.initials: A
authors.lastname: Bergquist
authors.forename: Rupesh
authors.initials: R
authors.lastname: Rajani
authors.forename: Stergios
authors.initials: S
authors.lastname: Kechagias
authors.forename: Björn
authors.initials: B
authors.lastname: Fischler
authors.forename: Antal
authors.initials: A
authors.lastname: Németh
authors.forename: Tomas L
authors.initials: TL
authors.lastname: Lindahl
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D019934:International Normalized Ratio / Q000295:instrumentation / Q000379:methods* / Q000592:standards; D007753:Laboratories; D008107:Liver Diseases / Q000097:blood* / Q000473:pathology*; D016031:Liver Transplantation / Q000379:methods* / Q000592:standards*; D008297:Male; D008875:Middle Aged; D011517:Prothrombin Time / Q000295:instrumentation / Q000379:methods; D012720:Severity of Illness Index; D055815:Young Adult
keywords: CV; EQUALIS; External Quality Assurance of Laboratory medicine; FII; FV; FVII; FX; INR; ISI; ISI(VKA); ISI(liver); Liver disease; Liver transplantation; MELD; PELD; PPP; PT; Prothrombin time; SSC; Severity of illness index; VKA; coefficients of variation; factor II; factor V; factor VII; factor X; international normalized ratio; international sensitivity index; international sensitivity index for patients on vitamin K antagonists; international sensitivity index for patients with liver disease; model of end-stage liver disease; pediatric end-stage liver disease; platelet poor plasma; prothrombin time; the Scientific and Standardisation Committee of the International Society on Thrombosis and Haemostasis; vitamin K antagonists