Packed Cell Volumes
Total Proteins and
Blood Films
Laboratory Procedures
PCV (Packed Cell Volume)
In a CBC, we determine the number of RBC’s in
several different ways. The quickest and easiest is
called the microhematocrit/hematocrit, also referred to
as the packed cell volume (PCV)
The PCV will tell you if the animal is anemic or
dehydrated.
Normal PCV Values
Canine: 37 – 55%
Feline: 30 – 45%
Equine: 32 – 52%
Bovine: 24 – 46%
Whole blood is collected in an anticoagulant (usually
EDTA) and placed in a capillary tube.
Microhematocrit tubes should be filled to the
designated line, with one end plugged with clay sealant.
Blood sample should be spun in a microhematocrit
centrifuge for 2-5 minutes
Lay the tube in the centrifuge with the plugged end
facing the outside of the centrifuge. Make sure that a
balancing tube is placed opposite or have another
sample across from yours.
Cells are heavier than plasma and are compacted at the
end of the tube that has the clay plug.
Reading your PCV
Plasma Evaluation
Plasma color and transparency may be helpful in
determining a diagnosis and should be recorded in
your findings.
Normal plasma is clear or a pale straw-yellow color
Cloudy Serum = lipemic
Reddish tinge = hemolyzed
Yellow = icteric (indicates possible liver disease)
Concentration of total protein / total solids
Plasma protein concentrations estimated by
refractometry is an important component of the CBC
in all species.
Plasma used to determine the TP/TS is collected by
breaking the hematocrit tube just above the buffy
coat/plasma interface.
The plasma is allowed to flow onto the refractometer.
(Blow gently through the open end of the hematocrit
tube with the broken end of the tube over the prism of
your refractometer.)
Hold the refractometer up to the light and record your
findings.
Make sure to wipe your refractometer after each use!
Blood Films
The blood film is used to perform the differential
WBC count; estimate platelet numbers; and evaluate
the morphological features of WBCs, RBCs and
platelets.
Wedge smears are prepared by placing a small drop of
blood on a clean glass microscope slide
Blood films
Staining a slide
Always stain using the lightest to darkest stain.
Remember which side of your slide is up (clothes pins are
marked “top”)
Rinse off from back side of slide
May heat fix to speed up process.
Performing the Differential Cell
Count
This is where the different white blood cells are
tallied separately. This can be done by a blood
counting machine, or by hand.
To manually count the different cells, first you must
make a perfect slide. Stain the slide once it is dry.
Using a cell counter you will tally a total of 100 cells
(this will make it easy to turn the numbers into a %)