THE USE OF THE WHOLE-BLOOD THROMBOTEST TIME (1/51) AS A ROUTINE MONITOR OF VITAMIN-K-DEPENDENT BLOOD-COAGULATION FACTOR LEVELS IN THE RAT

The widespread use of the one-stage prothrombin time as a measure of vitamin K-dependent coagulation factors in humans has, for many years, been extended to rodents during toxicity studies. However, the large blood sample required and the method's relatively low sensitivity when using certain commercially available rabbit brain thromboplastins make an alternative desirable. We found that the thrombotest clotting time (1/51 method) is much more sensitive than the prothrombin time in detecting depletion of the vitamin K-dependent coagulation factors in rats. Furthermore, the small volume of blood required (10-mu-l) makes this a highly suitable alternative.