Diffraction measurement of erythrocyte sedimentation rate

We propose a new method to measure the erythrocyte sedimentation rate (ESR). In clinical practice, the ESR is determined by visual inspection of the fall of blood/plasma boundary. The test applied to the blood of patients with polycythemia vera gives low or zero sedimentation rate. It is shown that in this case the upper boundary of the container and the frontier of the red blood form a slit filled with plasma. Diffraction of laser light by the slit was investigated. Intensity distributions of the diffraction pattern were measured during the sedimentation process. The ESR was determined from the temporal dependence of the position of successive intensity maxima of the diffraction pattern. The sedimentation curves signalise the existence of two phases of the blood formed in the process.