Significance of Local International Sensitivity Index Systems for Monitoring Warfarin and Liver function

Abstract

Local ISI determined by a commercial local calibrator improved INR standardization among thromboplastins. The alternative ISI calibration using liver-specific calibration plasma is expected to reduce INR variability for the evaluation of liver function.

The international normalized ratio (INR): What reagent, what instrument? The assessment of the agreement between INR values according to different reagent/instrument combinations

“…1,2 With the automatization of laboratories, several studies have shown that the ISI of thromboplastin may also vary, depending on the instrument used. Consequently, a reagent-or instrument-specific ISI was introduced.…”

“…In addition, it has been suggested to determine the local ISI for each reagent/instrument combination. 1 Currently, biologists often wish to know whether changing the instrument or the reagent has any impact on INR results. As there is no "reference" combination, a new one must be compared to the older one.…”

“…In routine hospital laboratories, the INR is either calculated using the ISI and the mean normal prothrombin time (MNPT) from the manufacturer or calibrated using a set of calibrators with assigned INR values. 1,2 With the automatization of laboratories, several studies have shown that the ISI of thromboplastin may also vary, depending on the instrument used. Consequently, a reagent-or instrument-specific ISI was introduced.…”

Monitoring of Anticoagulant Therapy

“…Procedures for using INR calibrants are described in CLSI document H-54 [9]. Local INR calibration using plasma calibrants is appealing from both a theoretical perspective and the documented deficiencies of the INR schema, and the use of INR calibrants improves INR accuracy and decreases interlaboratory variation [11][12][13][14][15][16][17]. However, calibrants are not available in the United States for most coagulation test systems.…”

Geração de trombina e efeito heparinoide endógeno em pacientes com cirrose antes e após o tratamento da infecção bacteriana

“…Este exame foi amplamente utilizado nas últimas décadas para avaliar e predizer o risco de sangramento em pacientes com cirrose, pois ele representa a redução dos níveis desses fatores procoagulantes na cirrose. A conversão dos resultados do TP para a escala international normalized ratio (INR) é validada apenas para a monitorização de pacientes em anticoagulação com antagonistas da vitamina K e o resultado está sujeito a ampla variabilidade (57,58) . Com o intuito melhorar a reprodutibilidade do INR em pacientes com cirrose, foi descrita uma padronização metodológica diferenciada, denominada na literatura de INR-Liver (59) .…”