Automated Cell Counters
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What are the advantages of automated cell counters over manual cell counting?
- More accurate results (many more cells are counted)
- Fast results
- Relatively simple to operate
- Perform multiple tests
What are the disadvantages of automated cell counters?
- Multiple sources of error (if you don't keep up with quality control)
- Species variations
- Down time problematic (technical support varies)
What are the three types of automated cell counters?
- Impedance (particle) counters
- Expanded buffy coat (QBC)
- Flow cytometry (Lasercyte)
Describe how the Impedance (particle) Counters work.
- Cells are suspended in electrolyte solution
- Electric current passses through the solution
- As cells pass through an aperture, it inhibits electrical conduction through the solution and then generates a pulse
- Pulse generated is related to the particle size
Describe how the QBC works.
- Blood is placed in a special tube that contains a powdered dye
- Add the float (this actually expands the buffy coat)
- Put the cap over the end
- Put the tube in the centrifuge at high speed
- As it spins, the cells settle during centrifugation based on their densities and the float present in the capillary tube expands the buffy coat by 10 times and the dye in the tube stains the cells
- The machine scans with UV light
- It records intensity of fluorescence of each layer (the thickness of the layers are converted to number quantities)
What are the layers of the QBC?
- Monocytes and lymphocytes
Describe how a Flow Cytometry Analyzers work.
- Cells pass through a laser beam
- Light is scattered, creating a specific pattern for each cell type
- Detectors note the pattern
What are the disadvantages of the Impedance Counter?
- No morphology
- No reticulocyte data
- Poor differentiation between the WBCs
- Counts any nucleated cell (NRBC) as a WBC
- Feline platelets (which are large) are counted as RBCs or even WBCs
- Fibrin strands clog the machine
What are the advantages of the QBC?
- efficient and economical (really cheap)
- Fast (about 7 minutes)
What are the disadvantages of the QBC?
- Designed to use with NORMAL blood
- Cannot tell lymphocytes from monocytes
- Cannot tell bands from segs
- Can only use for certain species
- Must fill capillary tube all the way
- Underestimates frequency of leukopenia
What are the advantages of the Flow Cytometry Analyzer?
- Ignores clumped cells
- Can differentiate large platelets (cats) from WBCs
- Does a 5-part differential, platelet count, reticulocyte count, and red cell indices
What are the disadvantages of the Flow Cytometry Analyzer?
- Aggregates (clumping) of platelets may be counted as WBCs
- More expensive
- Examination of a blood film is still always needed to detect morphology
What are the advantages of using a commercial lab?
- Cheaper than in-house
- State-of-the-art equipment
- Quality control programs
- Films evaluated by experienced personnel
- Consultation with pathologist
What are the disadvantages of using a commercial lab?
- Takes time to get results
- Make blood smears immediately, send along with EDTA blood
- Species specificity (human labs)
What is automated cell counting?
- Use for WBC count
- Should never replace looking at a blood smear
- Many give RBC count and red cell indicies as well
Can an automated cell counter give you the same information that reading a blood smear gives you?
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