Switch to the high-power lens and count
the number of cells in field 1. Move the
hemacytometer until field 2 is in focus and
repeat the counting procedure. Continue
until the cells in all five fields have been
counted. Note that the fields are numbered
clockwise around the chamber, with field
5 being in the center. Count the fields in
this order. To count the cells in each field,
start in the upper left small square and
follow the pattern indicated by the arrow
in figure 6-8. Count all of the cells within
each square, including cells touching the
lines at the top and on the left. DO NOT
COUNT ANY OF THE CELLS TOUCH-
ING THE LINES ON THE RIGHT AND
AT THE BOTTOM.
Total the number of cells counted in all five
fields and multiply by 10,000 to arrive at
the number of red cells per cubic millimeter
of blood. The number of cells counted in
each field should not vary by more than
20. A greater variation may indicate poor
distribution of the cells in the fluid,
resulting in an inaccurate count.
Immediately after completing the count,
clean the counting chambers with distilled
water and dry it with lens tissue. Rinse
pipettes first with cold water, then with
acetone. Draw air through the pipette until
it is dry. The pellet should move freely in
the bulb if the pipette is dry.
Some common sources of error are:
Improper dilutionnot drawing blood ex-
actly to the 0.5 mark or using too much
Dirty equipmentdiluting fluid unfiltered;
greasy glassware; dirty microscope; wet
Poor mixing or not discarding first few
drops of fluid
Poorly loaded counting chamber
Chipped pipettes. Discard pipettes with
chipped or broken tips.
Use of gauze, cotton, or filter paper to
remove excess blood from the pipette.
The Uniopette disposable diluting pipette
system for the red blood cell count provides a
convenient, precise, and accurate method for ob-
taining a red blood cell count. The disposable kit
consists of a shielded capillary pipette (10
microliter (ul) capacity) and a plastic reservoir
containing a premeasured volume of diluent
Using the shield on the capillary pipette,
puncture the diaphragm in the neck of the
reservoir with the tip of the capillary shield.
After obtaining free-flowing blood from a
lancet puncture of the finger, remove the
protective plastic shield from the capillary.
Holding the capillary slightly above the
horizontal, touch the tip to the blood
source. Capillary action will fill the tube
until blood collection stops automatically,
e.g., when the proper amount (10 ul) has
been obtained. Wipe blood off the outside
of the capillary tube, making sure none is
removed from inside the capillary tube. An
alternative source of blood is a thoroughly
mixed fresh venous blood sample obtained
Squeezing the reservoir slightly, cover the
upper opening of the capillary overflow
chamber with the index finger and seat the
capillary tube holder in the reservoir neck.
Release pressure on the reservoir and re-
move the finger from the overflow
chamber opening. Suction will draw the
blood into the diluent in the reservoir.
Squeeze the reservoir gently two or three
times to rinse the capillary tube, forcing
diluent intobut not out ofthe overflow
chamber, releasing pressure each time to
return diluent to the reservoir. Close the
upper opening with your index finger and
invert the unit several times to mix the
blood sample and the diluent.
For specimen storage, cover the overflow
chamber of the capillary tube with the
Immediately prior to cell counting, mix
adequately again by gentle inversion, tak-
ing care to cover the hole with your index
Remove the pipette from the reservoir.
Squeeze the reservoir and reseat the pipette
in the reverse position, releasing pressure
to draw any fluid in the capillary tube into
the reservoir. Invert and fill the capillary
tube by gentle pressure on the reservoir.