A comparison of five commercial thromboplastins: ISI re-evaluation on an automated coagulometer

Five commercial rabbit brain thromboplastins were compared with an International Reference Preparation on an ACL coagulometer, using 90 patients stabilized on warfarin and 22 normal individuals. The prothrombin times were converted to INRs using the thromboplastin manufacturers' quoted ISI. The...

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Bibliographic Details
Published inClinical and laboratory haematology Vol. 17; no. 1; p. 41
Main Authors Ford, K, McArdle, B, Kesteven, P J
Format Journal Article
LanguageEnglish
Published England 01.03.1995
Subjects
Animals
Blood Coagulation - drug effects
Blood Coagulation Tests - instrumentation
Blood Coagulation Tests - standards
Brain Chemistry
Calibration
Humans
Prothrombin Time
Rabbits
Reference Standards
Thromboplastin - analysis
Thromboplastin - chemistry
Thromboplastin - isolation & purification
Warfarin - pharmacology
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Summary:Five commercial rabbit brain thromboplastins were compared with an International Reference Preparation on an ACL coagulometer, using 90 patients stabilized on warfarin and 22 normal individuals. The prothrombin times were converted to INRs using the thromboplastin manufacturers' quoted ISI. The quoted ISIs were reassigned using orthogonal regression analysis and then used to recalculate INRs for patient and commercial INR control plasmas. This showed that the manufacturers' quoted ISIs and the INR control plasma results were inconsistent. With one thromboplastin the manufacturers quoted ISI changed from 1.17 to 1.05 whilst the control plasma results changed from an INR of 4.3 to an INR of 3.7 (manufacturer's INR, 3.3). In most routine laboratories ISI reassignment is not practical. We conclude that the availability of a reliable plasma calibrant is essential for the accurate calculation of INRs at a local level.
ISSN:0141-9854
DOI:10.1111/j.1365-2257.1995.tb00315.x