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Simplified Method for Local Correction of System International Normalized Ratio
1Department of Hematology, Apollo Hospitals, Chennai, India.
Laboratory Medicine
|September 22, 2017
Abstract
Background:
International normalized ratio (INR) derivation is dependent on the international sensitivity index (ISI) of thromboplastin. It varies with instrument and reagents used.
Objective:
To evaluate the role of a correction factor in the derivation of INR.
Methods:
We studied prothrombin time (PT) and INR from patients using 3 thromboplastins of varying ISI values. The correction factor was applied to the observed INR to obtain a corrected INR.
Results:
The difference between corrected INR and observed INR values varies from -0.8 through 0.96.
Conclusions:
Corrected INR is dependent on PT only. It can be applied to all patients irrespective of cause for elevated PT.