The page below is a sample from the LabCE course Dermal Puncture and Capillary Blood Collection. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Hematology Specimens

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 size of the drop that should be used.

Using a second glass slide, the phlebotomist should spread the blood by first aligning the edge of the spreader slide in front of the drop of blood, pulling 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 an angle of approximately 20° 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 sealing clay or commercially-provided covers that are made specifically for the microhematocrit system that is in use.

Capillary tubes should be plastic or mylar-wrapped glass tubes. Plain glass capillary tubes should not be used to prevent the possible transmission of bloodborne pathogens if the tube broke and punctured through the glove and skin of the phlebotomist.

It is imperative that the specimens are labeled appropriately with patient information. This can be accomplished by inserting the capillary tubes into a second larger blood collection tube that is labeled with the patient name and second identifier, such as hospital or medical record number and capping the large tube. Taping the capillary tubes individually to a paper requisition with the patient information is an alternate method.