international sensitivity index


international sensitivity index (ISI),

the slope of the line of best fit relating the log prothrombin time obtained with a standard reagent to the log prothrombin time obtained with the working reagent for both normals and patients who receive stable oral anticoagulant therapy; the standard reagents used for this value assignment are reference preparations calibrated against the World Health Organization standard reagent. Compare: international normalized ratio.

international sensitivity index

Hematology A measure of thromboplastin-activating capacity, or the sensitivity of a thromboplastin reagent to anticoagulation. See International normalized ratio.

in·ter·na·tion·al sen·si·ti·vi·ty in·dex

(ISI) (in'tĕr-nash'ŭn-ăl sen'si-tiv'i-tē in'deks) The slope of the line of best fit relating the log prothrombin time obtained with a standard reagent to the log prothrombin time obtained with the working reagent for both normal people and patients who receive stable oral anticoagulant therapy; the standard reagents used for this value assignment are reference preparations calibrated against the World Health Organization standard reagent.
See also: international normalized ratio

International Sensitivity Index

Abbreviation: ISI
A laboratory standard for thromboplastins, the reagents used to determine the prothrombin time (PT). Because thromboplastin contents vary, PT results performed on the same sample of blood in different laboratories can be markedly different, even though the patient's actual level of anticoagulation is a constant. The ISI is used to calculate the international normalized ratio, a standardized measure of anticoagulation, thus enabling health care professionals working with different laboratories to compare results and adjust anticoagulant doses according to a single set of guidelines. See also: index