Final answer:
The correct order for a technician to collect blood samples using one needle for both a clotted sample and a heparinised sample is to collect the red top tube first and the green top tube second, to prevent cross-contamination and ensure accurate test results.
Step-by-step explanation:
When collecting blood samples for CBC and serum analysis requiring both a clotted sample (red top tube) and a sample mixed with anticoagulant heparin (green top tube), the proper order is critical. The technician should collect the red top tube first, as it does not contain anticoagulant and allows the blood to clot for serum analysis. Following this, the green top tube, which contains heparin, an anticoagulant, should be collected second. This sequence prevents the contamination of the clotting tube with anticoagulant, which could otherwise compromise the integrity of the serum analysis.
In more detailed phlebotomy practices, technicians adhere to a specific order of draw, typically based on the additive the tube contains. This order is essential to prevent cross-contamination of tube additives, which may interfere with test results. For the given question, the answer is D. Red top 1st, green top 2nd. By following this sequence, the integrity of both the clotted sample for serum analysis and the anticoagulant-preserved sample for the CBC is maintained.