Which laboratory technique detects the number of cells in a sample based on electrical impedance?

The technique that detects the number of cells in a sample based on electrical impedance is the Coulter counter. This method operates on the principle that as cells pass through an aperture, they cause changes in electrical resistance. The instrument measures these changes, allowing it to count the number of cells and even determine their size. The use of electrical impedance provides rapid and accurate counts of cells in a sample, making this technique especially valuable in hematology for analyzing blood samples.

Flow cytometry, while also used for counting cells, relies on laser technology and fluorescent markers to analyze physical and chemical characteristics as cells pass through a laser beam. Microscopy involves visually counting cells through a microscope but does not provide an automated or quantitative measurement like electrical impedance does. Enzyme-linked immunosorbent assay (ELISA) is a technique focused on detecting and quantifying proteins or antigens rather than counting cells. Thus, the Coulter counter is the appropriate choice for detecting the number of cells based on electrical impedance.