APPARATUS AND METHOD FOR SEDIMENTATION BASED BLOOD ANALYSIS

An apparatus and process for accurately determining settling data for the settling of erythrocyte cells from a plasma fluid in a test specimen of blood. The apparatus includes a settling tube, a sensing assembly movably mounted proximate the settling tube. Preferably an infrared emitter and detector are provided in the sensing assembly, and a control assembly is provided which senses data at a high rate and is responsive to the sensed data to sample or store the time at which sensed reflectivity exceeds a threshold level. When the threshold is reached, data is sampled and the tracking head is moved by a very small step. This process is repeated to enable tracking of the descent of the separation boundary between the erythrocyte cells and plasma fluid. The apparatus senses changes in reflectivity of the erythrocyte portion of the specimen below and up to the separation boundary. The apparatus and process also includes a scanning process to calibrate the reflectivity for each test specimen, the reflectivity also is measured immediately after moving the sensing assembly and recorded as a function of the position of the sensing assembly. An apparatus and process for scanning the plasma fluid and white cells above the separation boundary for reflectivity of infrared or visible light radiation as a function of height above the separation boundary also is disclosed.