Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which blood collection tube is used for a "crossmatch"?

1. Lavender

2. Light blue

3. Gray

4. Green

The correct answer is: Lavender

For a "crossmatch," the appropriate blood collection tube is the lavender-top tube, which contains EDTA as an anticoagulant. This tube is specifically used for blood typing and crossmatching because the EDTA preservative helps maintain the integrity of the blood sample by preventing clotting. The preservation of cellular components and plasma proteins is crucial for accurate testing in crossmatch procedures, where compatibility between donor and recipient blood is assessed before a transfusion. The use of lavender tubes helps ensure that the results reflect the true immunological response and hemagglutination potential of the blood. While other tubes have specific uses, they do not provide the suitable conditions needed for crossmatching. For example, light blue tubes are typically used for coagulation studies, gray tubes might be used for glucose and lactate measurements, and green tubes are often utilized for tests requiring heparin. Each of these has properties that are not ideal for the stability and viability of blood for crossmatching purposes.