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Hematology analyzers are used to conduct a complete blood count (CBC), which is usually the first test requested by physicians to determine a patient's general health status. [5] A complete blood count includes red blood cell (RBC), white blood cell (WBC), hemoglobin, and platelet counts, as well as hematocrit levels.
Celloscope automated cell counter was developed in the 1950s for enumeration of erythrocytes, leukocytes, and thrombocytes in blood samples. [1] Together with the Coulter counter, the Celloscope analyzer can be considered one of the predecessors of today's automated hematology analyzers, as the principle of the electrical impedance method is still utilized in cell counters installed in ...
The Coulter principle states that particles pulled through an orifice, concurrent with an electric current, produce a change in impedance proportional to the volume of the particle traversing the orifice. This pulse in impedance originates from the displacement of electrolyte caused by the particle.
The Coulter principle uses electrical impedance measurements to count blood cells and determine their sizes; it is a technology that remains in use in many automated analyzers. Further research in the 1970s involved the use of optical measurements to count and identify cells, which enabled the automation of the white blood cell differential.
Blood is sampled and diluted, and moves through a tube thin enough that cells pass by one at a time. Characteristics about the cell are measured using lasers (fluorescence flow cytometry) or electrical impedance. Because not everything about the cells can be measured at the same time, blood is separated into a number of different channels.
Electrical analysis involves passing a dilute solution of the blood through an aperture across which an electrical current is flowing. The passage of cells through the current changes the impedance between the terminals (the Coulter principle). [6]
The first impedance-based flow cytometry device, using the Coulter principle, was disclosed in U.S. Patent 2,656,508, issued in 1953, to Wallace H. Coulter.Mack Fulwyler was the inventor of the forerunner to today's flow cytometers – particularly the cell sorter. [6]
Flow cytometry is by far the most sophisticated and expensive method for cell counting. In a flow cytometer the cells flow in a narrow stream in front of a laser beam. The beam hits them one by one, and a light detector picks up the light that is reflected from the cells.