Electrical Impedance and Colorimetric Measurements. Joanna Ellis, MLS(ASCP). Objectives. Cite the electrical impedance principle of cell counting. Identify and interpret microcytic and macrocytic RBC histograms Define coincidence
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Electrical ImpedanceandColorimetric Measurements
Joanna Ellis, MLS(ASCP)
Sweep Flow: Steady stream of diluent that flows behind each aperture to prevent cells from re-entering the aperture
The black line represents normal cell distribution. The red line on the RBC histogram graphically represents a microcytic red cell population.
Coincidence: Multiple cells passed through the aperture at once.
Aperture in electric field
In some analyzers the WBC count is directly measured by electric impedance after the red cells have been destroyed by a lysing agent. The lysing agent also shrinks the leukocyte cell membrane and cytoplasm; therefore, the WBC count represents the measure of the cell volume not native cell size. Colorimetric measurements are used to determine hemoglobin.
Mononuclear Cells: 92-152 fL
Granulocytes: 152-450 fL