Patent ID: 7901694

Claim:
A method for determining a coagulation parameter for a blood or blood component of a living being, comprising: reacting a sample of blood or a blood component containing fibrinogen with a clotting agent that transforms fibrinogen to fibrin by combining said blood sample with said clotting agent; recording, with recording means for making optical measurements, time and optical density values for the sample that correspond with the optical activity of fibrinogen activity during the reaction with the clotting agent, wherein optical density values plotted at their respective corresponding times over the course of the reaction represent a clotting curve; determining a slope corresponding with the maximum acceleration rate of transformation of fibrinogen to fibrin during the clotting reaction; determining an end of test time (TEOT) corresponding with an optical density value (cEOT) that is indicative of a substantial completion of the reaction of the fibrinogen of the sample and the clotting agent, wherein said time (TEOT) corresponds with the time at which a line of said slope that represents the rate of maximum acceleration of the clotting activity based on the optical activity of the clotting reaction intersects said optical density value (cEOT); determining the optical density value (c 1 ) at the time the sample and the clotting agent combined therewith begin to form a change in clotting activity (T 1 ); determining a time to maximum acceleration (Tmap) of the clotting reaction for the transformation from fibrinogen to fibrin in the sample; recording the optical activity value (c TMAP ) at the time of maximum acceleration (Tmap); determining an INR value, INRn, for the sample, wherein INRn corresponds with a trapezoidal area defined by the clotting curve and is expressed by the following relationship: INRn=((T 1 +TEOT)/2)*MUL*Tmap, where (MUL) is a multiplier that relates the sampling rate at which time and optical activity measurements are recorded with the pixel parity of the x-y axis of the clotting curve.