Coagulation
Coagulation laboratory tests
International sensitivity index (ISI)
Author: Jeremy C. Parsons, M.D.
Last author update: 1 November 2012
Last staff update: 22 September 2020
Copyright: 2002-2024, PathologyOutlines.com, Inc.
PubMed Search: International sensitivity index [title]
Table of Contents
Definition / generalCite this page: Parsons JC. International sensitivity index (ISI). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/coagulationISI.html. Accessed April 23rd, 2024.
Definition / general
- Measure of sensitivity of particular PT reagent - determined by manufacturer
- Used to resolve interlaboratory variations in PT (Arch Pathol Lab Med 2004;128:308, J Clin Pathol 2003;56:114)
- 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
