PROTHROMBIN TIME IN LIVER-FAILURE - TIME, RATIO, ACTIVITY PERCENTAGE,OR INTERNATIONAL NORMALIZED RATIO

Prothrombin time (PT) dis a universal indicator of liver disease sever ity, However, variability in thromboplastin reagents leads to large in terlaboratory differences in PT results, The aim of this study was to determine whether the use of the international normalized ratio (INR) or other modes of expression might achieve PT standardization in patie nts with liver failure, PT was measured with seven thromboplastin reag ents with different sensitivities in plasmas from 27 patients with mis cellaneous chronic and acute Liver failure and, as a control populatio n, 29 patients on oral anticoagulation therapy. PT was expressed in se conds, ratio, activity percentage, and INR. In patients with liver fai lure, only activity percentage expression eliminated variability in PT results obtained with the seven thromboplastins while INR, seconds, a nd ratio values remained significantly different (P < .01), In patient s on oral anticoagulant therapy, only INR normalized PT results, We co nclude that, in patients with liver failure, INR fails to yield a PT e xpression independent of the thromboplastin used and only activity per centage expression may provide a common international scale of PT repo rting.