title: INR derivation with the PT/INR Line simplified using a spreadsheet from the world wide web.
abstract: BACKGROUND
  The prothrombin time/international normalised ratio (PT/INR) Line method to derive INR, based on only five European Concerted Action on Anticoagulation (ECAA) certified plasmas, is shown to be reliable in previous ECAA studies. A simpler method not requiring linear regression calculation would be an advantage.
  
  
  METHODS
  After determining the local PT/INR Line, local INRs have been obtained using a readily available spreadsheet on the internet which laboratories can use without performing any additional calculations.
  
  
  RESULTS
  Examples of INR derivation have been obtained from results at 16 centres using a range of local coagulometers with human thromboplastin international reference preparations (IRPs). The procedure does not require manual PT testing, local international sensitivity index calibration, availability of thromboplastin IRPs or local mean normal prothrombin time.
  
  
  CONCLUSIONS
  From the PT/INR Line, INR values for local PT results are easily obtained using an Excel spreadsheet from our website (http://www.anticoagulants.co.uk/) which does not require the complex linear regression analysis to derive INR.
authors.affiliation: EAA Central Facility, Faculty of Life Sciences, University of Manchester, Manchester, UK. leon.poller@manchester.ac.uk
authors.forename: Leon
authors.initials: L
authors.lastname: Poller
authors.forename: Saied
authors.initials: S
authors.lastname: Ibrahim
authors.forename: Albert
authors.initials: A
authors.lastname: Pattison
authors.forename: Jørgen
authors.initials: J
authors.lastname: Jespersen
mesh_terms: D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage*; D001777:Blood Coagulation / Q000187:drug effects*; D002138:Calibration; D016903:Drug Monitoring / Q000379:methods* / Q000592:standards; D006801:Humans; D019934:International Normalized Ratio / Q000592:standards; D020407:Internet; D016014:Linear Models; D011517:Prothrombin Time / Q000592:standards; D015203:Reproducibility of Results
chemical_list: D000925:Anticoagulants