American Society for Clinical Pathology (ASCP) Histotechnician Certification Practice Exam

If a phlebotomist collects a blood sample for an ACT but does not mix the tube, what is the likely outcome of bedside testing?

1. Decreased coagulation time

2. No effect on results

3. Increased coagulation time

4. Unstable sample

The correct answer is: Increased coagulation time

In the context of blood collection and testing for activated clotting time (ACT), proper mixing of the collected sample is crucial for ensuring accurate results. When a blood sample is drawn into a tube containing an anticoagulant, such as sodium citrate, it is essential to mix the sample immediately to prevent clot formation. If the tube is not mixed appropriately, the anticoagulant will not evenly interact with the blood, leading to an inconsistent sample. As a result, the clotting factors may remain activated in areas where the anticoagulant has not been sufficiently mixed, while other areas remain unaffected. This inconsistency can cause a prolonged response in the test due to the uneven distribution of the anticoagulant. Consequently, the testing may show an increased coagulation time, as the sample may not accurately reflect the patient’s true coagulation status due to clotted segments affecting the results. In this scenario, "increased coagulation time" is the likely outcome of bedside testing when the tube is not mixed, as the sample's integrity is compromised, leading to erroneous or unreliable results.