The tube used for a Complete Blood Count (CBC) is an EDTA tube, which has a purple top.
Understanding CBC Tubes
A CBC is a common blood test that provides important information about your blood cells. The specific tube used for collecting the blood sample is crucial for the accuracy of the results. Here's a breakdown of why EDTA tubes are used:
EDTA Tubes (Purple Top)
- Anticoagulant: EDTA (ethylenediaminetetraacetic acid) is an anticoagulant. It prevents blood from clotting by binding to calcium, which is necessary for the clotting process.
- Preservation of Cells: The use of EDTA allows the blood cells to be preserved in their natural state, which is vital for accurate analysis.
- Differential Requirement: When a differential count (identifying different types of white blood cells) is required as part of a CBC, slides need to be prepared within 12 hours of blood collection according to the reference provided.
- Stability: Refrigerated EDTA blood is stable for a CBC for up to 24 hours.
- Unacceptable Specimens: Clotted or hemolyzed specimens are not suitable for CBC testing.
Why Purple Top Tubes are Preferred for CBC
- Accuracy: EDTA is the preferred anticoagulant for CBC because it doesn't alter the morphology of the blood cells, ensuring the count is accurate.
- Consistency: Using the correct tube helps maintain consistency and comparability of results across different tests and labs.
Practical Insights and Examples
- Slide Preparation: When a white blood cell differential is needed, making slides within 12 hours is crucial to prevent any change in the cell morphology which can lead to inaccurate results.
- Refrigeration: Refrigerating samples that require testing within 24 hours after blood collection can prolong their stability.
- Proper Specimen Handling: Clotted or hemolyzed samples are not acceptable because they interfere with the testing process, potentially leading to inaccurate results.
- Best Practices: Always follow the lab's specific guidelines for blood collection and handling.
| Tube Type | Anticoagulant | Use |
|---|---|---|
| Purple Top | EDTA | CBC, Blood differential |
