8-57
What You Need: A WBC Unopette, a hemacytometer with coverslip, a microscope, a tally counter, a
moisture chamber, a clock, a laboratory request form, and a logbook.
What To Do:
- Inspect the equipment.
a. Check the hemacytometer and coverslip for nicks, scratches, and cleanliness. Replace if
necessary.
b. Verify that the WBC Unopette reservoir and capillary pipet are in usable condition.
c. Verify that the tally counter is operable; if not, replace it. - Prepare the blood for the count.
a. Puncture the Unopette reservoir with the protective shield over the capillary pipet.
b. Touch the tip of the capillary pipet to the blood specimen and allow the pipet to fill by capillary
action.
NOTE: The filled capillary pipet must be free of bubbles.
c. Wipe excess blood from the outside of the pipet without touching the tip.
d. Squeeze the reservoir slightly, cover the overflow chamber of the pipet with the index finger, and
insert the capillary pipet into the reservoir.
e. Simultaneously, remove the finger from the overflow chamber and release pressure from the
reservoir to draw the blood into the diluent.
f. Squeeze the reservoir several times to rinse the pipet and to thoroughly mix the blood with the
diluent.
g. Let the reservoir stand for at least 10 minutes to allow the red cells to hemolyze.
NOTE: The leukocyte count should be performed within 3 hours of collection. - Prepare the diluted specimen for count.
a. Mix diluted blood by inverting the reservoir to resuspend the cells.
b. Convert to a dropper assembly by withdrawing the pipet from the reservoir and reseating it securely
with the capillary tube exposed.
c. Clean the capillary bore by inverting the reservoir and gently squeezing the sides to discard 3
to 4 drops. - Prepare the hemacytometer.
a. Charge both sides of the hemacytometer by gently squeezing the sides of the reservoir
to expel the contents until the chambers are properly filled.
b. Place the hemacytometer in a moist chamber (Petri dish containing a damp gauze pad).
c. Allow the cells to settle for 3 to 5 minutes. - Perform a WBC count.
a. Check under low power, low light for even distribution of cells.
b. Count all 9 square millimeters of the counting chamber. Count the WBCs lying within the square
and those touching the extreme upper and far right lines.
NOTE: There should be no more than a 10 cell difference among the 9 squares counted.
c. Count the second chamber in the same manner.
NOTE: There should be no more than a 15 cell difference between the two sides of the chamber. - Calculate the WBC count
a. Add up the total number of WBCs in both counting chambers.
b. Divide the sum by two to get the average number of cells counted.
c. Use the following formula to obtain the WBCs/L:
FORMULA: Avg # cells counted x âKâ factor x 1,000,000 (10 to the 6th power) = WBCs/L.
K FACTOR:
Dilution factor = 100
Area factor = 0.111
Depth factor = 10