UNIT 1 - Lecture 2: Evaluating Erythrocytes Flashcards
What does a hemocytometer do and when is it helpful?
Provides manual cell count for blood;
Helpful for low cellularity cytology (i.e. CSF) - <1000 cells/µL
For what spp is a hemocytometer necessary?
Spp with nRBCs (birds, reptiles, fish)
What is the impedance method?
Uses changes in electrical resistance to count cells and can provide an assessment of cell volume
What are the 3 steps to the impedance method?
- Constant electrical current applied across an aperture
- Cells suspended in saline move through the aperture “single file”
- Cells pass through aperture –> impedance altered –> voltage pulse generated (# pulses = cell #, amplitude = cell volume)
What are the 2 steps to flow cytometry?
- Cells pass through laser in “single file”
- Light scatters at different angles, which is detected by instrument (–> cell #, volume, complexity)
What 4 things does a CBC do?
- Assesses total RBC mass in peripheral blood (Hct/PCV, [RCB], [Hgb])
- Describes the RBC population (MCV, MCH, MCHC, RDW)
- Assesses regeneration (retic%, retic absolute)
- Evaluates RBC morphological changes (blood smear)
What is [RBC] and what is it used for?
RBCs / unit volume of blood
Used to calculate MCH, +/- MCV
What is PCV AKA?
spun hematocrit
What is PCV?
Packed cell volume;
% of blood comprised of RBCs
What does a low PCV mean? High?
Low = anemia
High = erythrocytosis
What is normal plasma color for cats/dogs? Horses/cattle?
Cats/dogs = colorless
Horses/cattle = light yellow
What does icteric plasma look like? Hemolytic? Lipemic?
Icteric = clear and bright yellow
Hemolytic = clear and pink to red (bc of free Hgb)
Lipemic = white and cloudy
What is Hct?
Hematocrit - calculated value, essentially the same as PCV
In animals with biconcave RBCs, the Hgb is ____ of the Hct.
~1/3
What are the 2 methods of measurement of Hgb? Which is more accurate?
- Direct spectrophotometric
- Optical measurement using laser light scatter (more accurate)
Direct spectophotometry to measure Hgb assumes that _____.
All Hgb is within cells
Optical measurement to measure Hgb measures ______.
Hgb content in RBCs directly
What things can interfere with measured [Hgb]?
Lipemia, Heinz bodies, oxyglobin (can falsely increase Hgb)
What condition is occurring when RBC count, PCV/Hct, and Hgb are low?
anemia
What condition is occurring when RBC count, PCV/Hct, and Hgb are high?
erythrocytosis