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Coagulation laboratory tests

International sensitivity index (ISI)

Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 10 February 2013, last major update November 2012
Copyright: (c) 2002-2013, PathologyOutlines.com, Inc.


● Measure of sensitivity of particular PT reagent - determined by manufacturer
● Used to resolve interlaboratory variations in PT (Arch Pathol Lab Med 2004;128:308 (ISI calibration), J Clin Pathol 2003;56:114 (ISI calibration for home PT monitors)
● Different PT reagents have different sensitivities to factor deficiencies
● High ISI (3.0) means insensitive reagent vs. low ISI (1.0) means sensitive reagent
● Labs should use reagents with an ISI of 1.0 to 1.5, if possible

End of Coagulation > Coagulation laboratory tests > International sensitivity index (ISI)

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