From Hematology Analyzers to Clinical Test Systems
Author: Narihiro OKU – The basic parameters for complete blood cell counts (CBC) contains the number of White blood cells (WBC), number and size of Red blood cells (RBC), the concentration of hemoglobin (Hgb) contained in the RBC, and the number of platelets (PLT). The clinical importance of the CBC is to diagnose and detect inflammation, anemia, hemostasis and many other disorders. For a long time, blood cells were counted manually using hemocytometer, thick glass microscope slide engraved with grooves creating a grid of perpendicular lines, and an optical microscope. In 1956, the Coulter Corporation developed an impedance method that dramatically improved the accuracy of these measurements. The basic concept of impedance method is to measure the voltage across an aperture in a constant electrical current. When a blood cell floating in saline solution passes through the aperture, the cell resistivity affects the voltage across the aperture, which enables to detect the existence of the cell.