In some institutions, the phlebotomist is responsible for collecting specimens that will be directly tested to yield results for hematology studies.
Blood Smear Films
If it is the practice of the institution, the phlebotomist may make a blood film slide directly from the blood flowing at a dermal puncture site. In this case, a drop of blood is allowed to fall directly onto the glass slide. The image below illustrates the approximate drop size that should be used.
Using a second glass slide, the phlebotomist should spread the blood by aligning the edge of the spreader slide in front of the drop of blood, pulling it back into the drop so that it is evenly distributed behind the spreader slide, as shown in the image below. Then spread the blood forward, maintaining a 30°-40° angle between the slides. The finished slide should be at least 2.5 cm in length, there should be a gradual transition in thickness from thick to thin, ending in a feather edge.
The blood smear should be made at the beginning of the dermal puncture procedure to avoid formation of microclots.
Remember that the glass slides used to make the blood smear are considered sharps and can cause accidental puncture injury to both the patient and the phlebotomist. Dispose of the spreader slide in a sharps container.
Also, until the smear is stained or fixed, the blood film is considered potentially infectious, so bloodborne pathogen precautions must be followed.
Microhematocrit collection
In some institutions, capillary blood specimens are collected directly into heparinized capillary tubes, which are then analyzed to determine packed cell volume. These results can be used to indicate the presence of anemia.
At least two capillary tubes should be filled for microhematocrit testing. The capillary tubes should be filled with blood to about two-thirds the length of the tube. One end of each tube should then be sealed to prevent blood from escaping. The sealant may be a commercially-provided cover made specifically for the microhematocrit system in use.
Capillary tubes should be plastic or wrapped glass tubes. Plain glass capillary tubes should not be used to prevent the possible transmission of bloodborne pathogens if the tube breaks and punctures through the glove and skin of the phlebotomist.
It is imperative that the specimens are labeled appropriately with patient information. The CLSI standards state that small, sealed capillary tubes from each patient should be placed into a single large test tube and then label the tube. Alternatively, when multiple capillary tubes are collected from a patient, the label can be placed around them, like a flag, and the labeled group is then placed into a large test tube. Taping the capillary tubes individually to a paper requisition with the patient information is an alternate method.
