list the order of draw in capillary blood collection and explain why it is important

list the order of draw in capillary blood collection and explain why it is important

The Correct Answer and Explanation is :

The order of draw in capillary blood collection is essential for ensuring that the samples collected do not get cross-contaminated, leading to inaccurate results. The correct order of draw is as follows:

1. Blood gases (if applicable)
2. EDTA (lavender or purple top tube): Used for hematology tests, such as complete blood counts (CBC).
3. Other additives (if applicable) (Green top for chemistry tests)
4. Serum tubes (Red or gold top tube): Used for tests that require a serum sample.
5. Heparin (green top tube): For tests that require plasma.

Explanation:

Capillary blood collection typically involves obtaining a sample from a fingertip or heel (in infants), using a lancet. The order of draw is important because of the potential for additive carryover, contamination between samples, and interference in test results.

1. Blood gases: If blood gas testing is required, it must be done first. Blood gases, such as pH, oxygen, and carbon dioxide levels, are very sensitive to contamination from other additives. Even trace amounts of anticoagulants or serum from other samples could alter these measurements.
2. EDTA tube: This is used for hematology tests, such as CBCs. EDTA is an anticoagulant that prevents blood clotting. Collecting EDTA samples before other tubes reduces the risk of clotting factors interfering with the other tests.
3. Other additives: Tubes that contain other additives (such as lithium heparin for chemistry tests) are drawn next. These additives prevent coagulation in samples and are specific for certain tests, so their order helps ensure that other tests don’t interfere with the analytes being measured.
4. Serum tubes: These tubes (red or gold top) do not contain any additives and are used for serum collection. Drawing them last minimizes the risk of additive contamination from previous tubes that could affect the quality of the serum.
5. Heparin: Finally, tubes containing heparin are used for plasma-based tests. Since they are the last in the order of draw, they avoid contamination from other substances.

Following the correct order ensures that accurate and reliable results are obtained, making it a critical practice in capillary blood collection.

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Here is an educational diagram illustrating the correct order of draw for capillary blood collection. It visually explains the sequence of tubes used and why the order is important. Let me know if you need further details or explanations!