Evaluation of an ultrasonic method applied to the measurement of blood coagulation time.

Clinical assessment of the blood clotting mechanism is usually made by measuring the time necessary for a sample of plasma to clot. In this work a semi-automatic method for measuring coagulation time is evaluated. It employs ultrasound, at 2.7 MHz, for monitoring variations of the viscosity in a plasma sample undergoing coagulation. The evaluation is performed by comparing measurements obtained by two well-known methods, the manual tilt tube and the fibrometer, with those obtained using the ultrasonic method. A total of 330 plasma samples from individuals with normal and altered homeostatic process were analysed. The experimental protocol follows two standard tests: the prothrombin time (141 samples) and the activated partial thromboplastin time (189 samples). The agreement between the three different methods is estimated statistically and it is shown that all the three can be used interchangeably for clinical purposes.