title: Significance of local international sensitivity index systems for monitoring warfarin and liver function.
abstract: OBJECTIVE
  Use of a local calibrator has been recommended for standardization of the international normalized ratio (INR) and international sensitivity index (ISI). We investigated the performance of two commercial local calibrators for warfarin monitoring and determined the significance of liver-specific INR.
  
  
  METHODS
  ISI values were determined using the World Health Organization (WHO) method and two commercial local calibrators. Liver-specific ISI was determined using plasma samples from patients with liver cirrhosis and normal controls.
  
  
  RESULTS
  In warfarin monitoring, the two local ISIs determined by the two local calibrators showed better consistency than uncorrected ISI, although they were inferior to the ISIs calibrated using the WHO method. Alternative calibration using calibration plasma from patients with liver cirrhosis instead of warfarinized plasma reduced the INR variability.
  
  
  CONCLUSIONS
  Local ISI determined by a commercial local calibrator improved INR standardization among thromboplastins. The alternative ISI calibration using liver-specific calibration plasma is expected to reduce INR variability for the evaluation of liver function.
authors.affiliation: Dept of Laboratory Medicine, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul 110-744, Korea; lukekhk@snu.ac.kr.
authors.forename: Hwa Jeen
authors.initials: HJ
authors.lastname: Lee
authors.forename: Ji-Eun
authors.initials: JE
authors.lastname: Kim
authors.forename: Hye Yeon
authors.initials: HY
authors.lastname: Lee
authors.forename: Hae Sook
authors.initials: HS
authors.lastname: Lim
authors.forename: Hyun Kyung
authors.initials: HK
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001779:Blood Coagulation Factors / Q000032:analysis; D002138:Calibration; D005260:Female; D006801:Humans; D019934:International Normalized Ratio / Q000592:standards*; D008103:Liver Cirrhosis / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011517:Prothrombin Time; D012015:Reference Standards; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D001779:Blood Coagulation Factors; D014859:Warfarin
keywords: Commercial local calibrator; International normalized ratio; International sensitivity index; Liver disease; Local calibration