Quick measurement of hematocrit and erythrocyte sedimentation-rate by means of a density tracking method.

An instrument to track the sedimentation properties of red blood cells quickly and automatically and to evaluate the hematocrit as well as the plasma density of a blood sample in the same operation is described. Erythrocyte-sedimentation basically is due to the density difference between the red blood cells and the plasma and the new method makes use of the mechanical-oscillator-technique, where the resonant frequency of the bending-type oscillations of a U-shaped glass tube is related to the density of the fluid with which the tube is filled. The oscillating U-tube is part of a sedimentation-tube of special dimensions and particular spatial orientation. The tube is tilted at 60 degrees, the tip of the U-tube being raised above the horizontal plane. Filling the sedimentation-tube with anticoagulated blood first permits recording of the density of the homogeneous suspension. Then, after a few minutes, the onset of erythrocyte-sedimentation produces a decrease in recorded density. The final value is related to the density of the supernatant plasma-fluid. Hematocrit, blood and plasma density of the undiluted blood sample as well as the sedimentation-rate of the anticoagulated sample are automatically calculated from the recorded sedimentation-curve. The particular arrangement of the tilted sedimentation-tube facilitates a determination of the maximum sedimentation-rate within 15 min at most.