While preparing to collect a blood specimen for a prothrombin time which of the following collection tubes should the phlebotomist use

Royal blue tubes are typically used for trace element testing and do not contain anticoagulants suitable for coagulation studies. They are designed to avoid contamination from other elements, making them inappropriate for tests like prothrombin time, where anticoagulant properties are necessary.

Red collection tubes generally have no additives or anticoagulants, allowing blood to clot naturally. Since prothrombin time tests rely on the measurement of clotting time in the presence of an anticoagulant, using a red tube would yield inaccurate results due to the lack of any substance that would prevent clotting.

Lavender tubes contain EDTA, an anticoagulant used primarily for hematology studies. While they are effective for preventing clotting, they are not suitable for coagulation tests like prothrombin time, which require a different anticoagulant to ensure that the test measures the clotting pathway accurately.