Using hydrodynamic focusing, the cells are sent through an aperture one cell at a time. During this, a laser is directed at them, and the scattered light is measured at multiple angles. The absorbance is also recorded. The cell can be identified based on the intensity of the scattered light and the level of absorbance.

How does a CBC machine work?

The CBC is performed using basic laboratory equipment or an automated hematology analyzer, which counts cells and collects information on their size and structure. The concentration of hemoglobin is measured, and the red blood cell indices are calculated from measurements of red blood cells and hemoglobin.

How are blood cells counted in a hematology analyzer?

With the hematology analyzer used at the Clinical Pathology Laboratory at Cornell University, red blood cells are sphered in a diluent and then passed through a laser light detector. The cells scatter light (at different angles) which is detected by the instrument (see image to the right).