CLINICAL LAB SCIENEC

358
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
12. Place a cover glass on a hemacytometer counting
chamber, making sure the glass is clean and grease
free. Although difficult, removal of fingerprints is
essential as they may cause problems with the
smooth filling of the chamber.
13. Remove the pipette from the reservoir. Squeeze
the reservoir and reseat the pipette in the reverse
position. Release pressure to draw any fluid in the
capillary pipette into the reservoir. Invert and fill the
capillary pipette by gentle pressure on the reservoir.
After discarding the first 3 drops in the pipette, load
(charge) the counting chamber of the hemacytometer
by gently squeezing the reservoir while the tip
of the pipette is touched against the edge of the
cover glass and the surface of the counting chamber
(Figure 13-19). A properly loaded counting chamber
should have a thin, even, and consistent depth of
fluid under the cover glass.
14. Allow 5 minutes for the cells to settle.
a. If fluid flows into the grooves (moats) at the
edges of the counting chamber or if air bubbles
FIGURE 13-19 Filling the hemacytometer using a
are seen in the field, the chamber is flooded and
Unopette capillary system.
must be cleaned with distilled water, dried well
Source: Delmar/Cengage Learning.
with lens paper, and refilled.
b. If the chamber is underfilled, carefully add more
fluid until the proper level is obtained.
15. Place the loaded hemacytometer in a petri dish on a moist circle of filter paper
and on two toothpicks or pieces of an applicator placed parallel on the paper. This
will help prevent the hemacytometer from becoming too wet for the microscope
stage. Wait at least 5 minutes for the cells to settle. The count should be initiated
no later than 10 minutes after the cells are placed on the counting chamber.
16. Once the cells have settled, ensure that the bottom of the hemacytometer is dry
and place the hemacytometer on the microscope stage. Using the low-power
objective, count the WBCs in the nine fields of the hemacytometer chamber. Each
field is composed of 16 small squares. To count the cells in each field, start in the
upper left small square. Count all of the cells within each square, including cells
touching the lines at the top and on the left. Do not count any cells that touch the
lines on the right or at the bottom. Repeat for each of the other eight fields.
17. When the cells in all nine fields are counted, calculate the result according to
Example 13-3, provided in the Reporting of Results section below.
18. Discard all supplies used for the procedure in the appropriate containers. A disinfectant
should be used to clean the work surfaces and equipment should be
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