8-55
NOTE: Negative pressure will draw blood into the reservoir.
(8) Squeeze the reservoir gently two to three times to rinse the capillary bore, forcing the diluent
up into (but not out of) the overflow chamber, releasing pressure each time to return the mixture
to the reservoir.
(9) Place the index finger over the upper portion of the opening and gently invert several times to
mix the blood thoroughly with the diluent.
(10) Let the mixture stand for 10 minutes before charging the hemacytometer.
(11) To charge the hemacytometer, convert the Unopette to a dropper assembly by withdrawing
the pipet from the reservoir and reseating it securely in the reverse position.
(12) Invert the reservoir and discard the first 3-4 drops of mixture before charging the
hemacytometer.
b. Prepare the blood for count using the pipet method.
(1) Draw blood to the 0.5 mark on the RBC pipet.
NOTE: The blood column must be free of bubbles.
(2) Wipe off any excess blood on the outside of the pipet tip.
(3) Do not touch the opening of the pipet with the wipe.
(4) Draw diluting fluid to the 101 mark.
(5) Wipe the outside of the pipet as in steps a (2) and a (3) above.
(6) Place the pipet between the thumb and forefinger and rotate it in a figure-of-eight motion for
3 minutes.
(7) Discard the first 2-3 drops of mixture before charging the hemacytometer.
- Prepare the hemacytometer.
a. Charge both sides of the hemacytometer.
b. Place the hemacytometer in a Petri dish.
c. Allow the cells to settle for 10 minutes. - Perform the RBC count.
a. Using low-power focus on the ruled section of the counting chamber, locate the center 1 square
millimeter area for counting RBCs.
b. Switch to high-power and locate the square in the upper left-hand corner.
c. Count all the RBCs lying within the square and those touching the centerline of the upper and
right-hand triple lines.
NOTE: RBCs touching the left-hand and bottom-center lines are not counted.
d. Count the remaining three corners and center.
e. If there is a variation of more than 25 cells between any of the five areas, repeat the test.
f. Count the second chamber in the same manner. - Calculate the RBC count.
a. Add up the total number of RBCs in both counting chambers.
b. Divide the sum by two.
c. Multiply by the K factor (constant) of 10,000.
d. Record the results as # RBCs X 10^12 RBC/L. - Perform a Wright’s stain of a blood sample (See Page 8-46).
- Recognize the significance of abnormal RBC morphology.
a. Anisocytosis: Variation in the size of the RBCs
(1) Macrocyte:
(a) Diameter: 9 microns or greater.
(b) May be found in liver disease.
(2) Microcyte:
(a) Diameter: 6 microns or less.
(b) Found in thalassemia and other anemias.
b. Poikilocytosis: Variation in the shape of the RBCs.
(1) Sickle shaped: associated with sickle cell disease.
(2) Ovalocytes/elliptocytes: associated with hereditary elliptocytosis.
(3) Spherocytes: