STEP 3: Collect the Blood.
Wipe away the first drop of blood. Place the collecting utensils into the drop
of blood, do not touch the skin. After the collection of the sample is
completed, have the patient hold a sterile gauze pad over the wound until the
Figure 2-2e. Wipe away the first
Figure 2-2f. Apply pressure to
drop of blood.
(1) Do not squeeze near the puncture area as this tends to shut off the blood
supply and dilute the blood with interstitial fluids.
(2) At the time of puncturing the skin, it is advisable to have the patient
looking away from the site, preventing a reflex pulling of the arm that may cause the
operator to stick his/her own finger.
2-10. PRESERVATION OF BLOOD
Anticoagulants are used to prevent clotting. Smears that are stained within a short
time after collection do not require fixation, but when a delay between collection and
processing occurs, methanol is the recommended fixative for the thin smears. Thick
smears should never be fixed. The anticoagulants routinely used in the laboratory do not
distort parasitic organisms to a great extent, but, nevertheless, direct smears are
The commonly used anticoagulants are divided into two groups: calcium binders
a. Calcium Binders. These anticoagulants prevent clotting by binding calcium
and thus preventing the complete chemical reaction that produces fibrin. Ethylene-
diamine-tetra-acetate (EDTA) is the most often used; others include sodium citrate,
sodium fluoride, and oxalates.