Final answer:
A phlebotomist should use a tube with sodium citrate for collecting blood for a PT/PTT test. Sodium citrate binds calcium needed for clotting, allowing accurate measurement of clotting time for the diagnosis of clotting disorders.
Step-by-step explanation:
The phlebotomist should use a tube with sodium citrate as the anticoagulant for a PT/PTT test. Sodium citrate is the preferred anticoagulant for coagulation studies because it preserves the coagulation factors and helps in obtaining a reliable result for the Prothrombin Time (PT) and the Partial Thromboplastin Time (PTT) tests. Both PT and PTT are essential tests that measure the time it takes for blood to clot and are used to diagnose clotting disorders.
While other anticoagulants like EDTA, potassium oxalate, and heparin are used for other types of tests, sodium citrate works best for PT/PTT because it binds calcium, which is necessary for the blood clotting process. Without calcium, the blood will not clot within the tube, allowing for accurate measurement of clotting time in the laboratory analysis.