NHA Phlebotomy Certification Practice Exam

What is the primary reason the order of draw for capillary collections differs from venipuncture?

1. Increased risk of contamination from skin

2. Higher likelihood of hematoma formation

3. Increased risk of coagulation due to platelet activation

4. More efficient blood collection procedure

The correct answer is: Increased risk of coagulation due to platelet activation

The order of draw for capillary collections differs from venipuncture primarily due to the increased risk of coagulation caused by platelet activation. In capillary blood collection, blood is drawn directly from a small puncture in the skin, which activates the platelets upon exposure to air and tissue. This activation can lead to clot formation more readily than in venous blood draws, where the blood encounters fewer traumatic factors. Because of this heightened activation of platelets, the components of the blood can vary significantly in specimens collected from capillary sources, particularly affecting tests that are sensitive to coagulation status. This necessitates a different order of draw to ensure the integrity of the samples and the accuracy of the tests performed, as certain additives present in collection tubes may interact differently when collected from capillary blood versus venous blood. Therefore, the order of draw is structured to minimize these risks and maintain the quality of the samples collected.