NHA Phlebotomy Certification Practice Exam

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Which of the following tubes is typically used for collecting blood for a Complete Blood Count (CBC)?

Red top
Green top
Purple top
Yellow top

The correct answer is: Purple top

The tube that is typically used for collecting blood for a Complete Blood Count (CBC) is the purple top tube. This type of tube contains an anticoagulant, often EDTA (ethylene diamine tetraacetic acid), which prevents the blood from clotting. The use of EDTA is crucial for a CBC because the test requires whole blood that maintains its cellular components in a liquid state for accurate analysis. This allows for reliable counts of red blood cells, white blood cells, and platelets, which are essential components assessed in a CBC. Other tubes such as the red top do not contain anticoagulants and are used for serum tests. The green top may contain heparin, which is suitable for specific tests, but it is not the standard for CBCs. The yellow top is often used for blood cultures and specific DNA tests. Each of these tubes serves a different purpose based on the type of test being conducted, emphasizing the importance of using the correct tube to obtain valid test results.