What automated cell-counting technique counts and sizes cells by pulse-height analysis?

Electrical Impedance is the Automated Cell-Counting Technique Using Pulse-Height Analysis

Electrical impedance is the automated cell-counting technique that counts and sizes cells by pulse-height analysis. This method measures changes in electrical resistance when cells pass through a small aperture, with the magnitude of the impedance change (pulse height) directly proportional to cell volume.

How Electrical Impedance Cell Counting Works

Electrical impedance cell counting operates on the Coulter principle, which involves:

1. Cells suspended in a conductive fluid pass through a small aperture
2. As each cell passes through, it displaces its own volume of electrolyte
3. This creates a measurable change in electrical impedance
4. The magnitude of this impedance change (pulse height) corresponds directly to cell size/volume
5. Analysis of these pulses allows for both counting and sizing of cells

Evidence Supporting Electrical Impedance as the Answer

The electrical impedance technique is widely recognized for its ability to count and size cells through pulse-height analysis. This technology:

• Provides true three-dimensional measurement of cells/particles 1
• Enables precise correlation between impedance changes and cell size/volume 1
• Achieves extraordinary precision and accuracy (approximately 98%) compared to manual and vision-based systems (75-80%) 1
• Reduces count interference from debris and clustering by calculating precise volumetric information 1

Advantages of Electrical Impedance Over Other Methods

Compared to Cytochemical Staining (Option A)

• Cytochemical staining identifies cellular components through specific chemical reactions but doesn't inherently count or size cells by pulse-height analysis
• Requires additional imaging or flow cytometry for quantification

Compared to Chromogenic Measurement (Option C)

• Chromogenic measurements detect color changes in reactions but don't directly measure cell size
• Cannot perform pulse-height analysis of individual cells

Compared to Optical Light Scatter (Option D)

• While optical light scatter can count cells, it measures light scattering properties rather than electrical impedance changes
• Though useful in flow cytometry, it doesn't specifically use pulse-height analysis based on electrical impedance

Clinical Applications of Electrical Impedance Cell Counting

Electrical impedance cell counting is used in various clinical and research settings:

• Complete blood counts in clinical laboratories
• Cell culture monitoring in research settings
• Quality control in industrial applications
• Determination of cell concentration and size distribution

Modern Implementations

Modern electrical impedance cell counters have evolved significantly:

• The CellSearch™ system utilizes electrical impedance principles combined with immunomagnetic separation 2
• Newer devices like the Moxi Z mini automated cell counter combine Coulter principles with thin-film sensor technology for precise sizing and counting 1
• Some systems incorporate coincidence correction algorithms to account for multiple cells passing through the aperture simultaneously 1

Potential Limitations

Despite its advantages, users should be aware of potential limitations:

• Requires cells to be in suspension
• May have difficulty distinguishing between cells of similar size
• Cannot provide information about internal cellular structures
• May be affected by cell aggregation or clumping

In conclusion, electrical impedance (option B) is clearly the automated cell-counting technique that counts and sizes cells by pulse-height analysis, as it directly measures changes in electrical resistance proportional to cell volume when cells pass through a sensing aperture.