NHA Phlebotomy Certification Practice Exam

Which tubes are used for capillary blood collection when WBC, RBC, and Electrolytes are ordered?

1. Blue and green

2. Gray and yellow

3. Lavender and red

4. Clear and orange

The correct answer is: Lavender and red

The choice of lavender and red tubes for capillary blood collection aligns with the types of tests being conducted, specifically for white blood cells (WBC), red blood cells (RBC), and electrolytes. Lavender tubes contain EDTA, an anticoagulant that is essential for hematological tests, as it preserves the integrity of blood cells by preventing clotting. This makes it ideal for counting and analyzing both WBC and RBC, since accurate cell counts are crucial for diagnosing various conditions. The red tube, often used for serum collection, does not contain any additives or anticoagulants, allowing the blood to clot. This is beneficial for tests that require serum, such as electrolyte analysis. When both hematological and serum chemistry tests are ordered together, these two tubes serve complementary roles. In capillary blood collection, due to the small volume of blood obtained, using these two tubes efficiently meets the testing requirements with appropriate preservation of the blood components needed for analysis.