Article Text
Abstract
A 10 centre calibration was performed after six years to determine the international sensitivity index (ISI) of rTF/95 relative to RBT/90, and to assess any international normalised ratio (INR) bias compared with the original multicentre calibration. After exclusion of one outlying centre, the follow up calibration gave a mean ISI for rTF/95 of 0.99, which although a small difference, is significantly greater than the mean ISI of 0.94 obtained previously. The change in ISI for international reference preparation (IRP) rTF/95 relative to RBT/90 would lead to a slight bias in INR for human compared with rabbit thromboplastins. At a theoretical INR of 3.0, the INR bias is 6.0%, and this is below the accepted 10% level of clinical relevance. Ongoing stability monitoring of World Health Organisation thromboplastin IRP is advised.
- CV, coefficient of variation
- ECAA, European Concerted Action on Anticoagulation
- INR, international normalised ratio
- IRP, international reference preparation
- ISI, international sensitivity index
- PR, prothrombin ratio
- PT, prothrombin time
- WHO, World Health Organisation
- international normalised ratio
- international sensitivity index
- multicentre calibration
- international reference preparation
Statistics from Altmetric.com
Footnotes
-
The study was supported by EC Standards, Measurements and Testing Programme (grant number SMT4-CT98-2269) and an additional research grant from the Manchester Thrombosis Research Foundation. Gratitude is expressed to WHO Biologicals for the supply of RBT/90 and rTF/95 IRP.