CLINICAL LAB SCIENEC

356
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
FIGURE 13-17 Parts of Unopette system used to dilute blood
sample for WBC and platelet counts.
Source: Delmar/Cengage Learning.
3. Disposable Unopette for WBC counts,
which consists of a shielded capillary
tube (20 μL capacity), and a plastic reservoir
containing a premeasured volume of
diluent (1:100 dilution) (Figure 13-17).
4. Clean hemacytometer and cover glass
5. Distilled water and lens paper for cleaning
hemacytometer
6. Blood specimens containing an EDTA
anticoagulant (or collect a fresh blood
sample following the process outlined in
Procedure # 3)
7. Brightfield microscope
8. Handheld counter
9. Petri dish with a moist circle of filter
paper and two toothpicks or pieces of an
applicator
10. Electronic timing device or clock/watch
with second hand
Procedure
1. Wash hands and don gloves.
2. Assemble necessary equipment and supplies.
3. Puncture the diaphragm in the neck of the reservoir with the tip of the capillary
pipette shield. Your instructor will demonstrate how to do this.
4. Remove the protective plastic shield from the capillary pipette.
5. Hold the capillary pipette apparatus slightly angled over a horizontal plane and
gently touch the tip to the blood source. The pipette should fill by capillary action
if the device is held at the correct angle. This may take some practice.
6. When blood reaches the end of the capillary bore in the neck of the pipette, the
pipette is completely filled and will stop automatically. The amount of blood collected
by the capillary pipette is 20 μL. Wipe any excess blood from the outside of
the capillary pipette while making sure none of the sample is removed by “wicking”
blood from inside the capillary pipette.
7. Between the thumb and forefingers of one hand, gently squeeze the reservoir
holding the diluent to force some air out, but do not expel any of the prepared
diluent. Maintain pressure on the reservoir. With the other hand, cover the upper
opening of the capillary overflow chamber with your index finger and seat the
capillary pipette holder in the reservoir neck.
8. Release pressure on the reservoir and remove your finger from the overflow
chamber opening. The suction will draw the correct amount of blood into the
diluent in the reservoir.
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