21. While preparing to collect a blood specimen for a prothrombin time which of the following collection tubes should the phlebotomist use
Answer: A
The phlebotomist should use a light blue collection tube for a prothrombin time specimen.
The light blue collection tube is specifically designed for coagulation studies, including prothrombin time tests, due to its sodium citrate additive, which ensures accurate results by binding calcium in the blood.
A) Light blue
This option is correct as light blue tubes contain sodium citrate, an anticoagulant that is essential for performing prothrombin time tests. The citrate prevents clotting and preserves the plasma for accurate measurement of coagulation factors.
B) Royal blue
Royal blue tubes are typically used for trace element testing or toxicology and do not contain any anticoagulants suitable for coagulation studies. Therefore, they are not appropriate for collecting specimens for prothrombin time.
C) Red
Red collection tubes are generally used for serum tests as they contain no additives to prevent clotting. Because prothrombin time requires an anticoagulant to preserve the sample, red tubes are not suitable for this purpose.
D) Lavender
Lavender tubes are used primarily for hematology tests, containing EDTA as an anticoagulant. While they are effective for certain tests, they are not the standard choice for prothrombin time, which specifically requires a light blue tube with sodium citrate.
Conclusion
The light blue collection tube is the definitive choice for collecting a blood specimen for prothrombin time due to its sodium citrate additive, which prevents clotting and maintains sample integrity. All other options fail to meet the necessary criteria for accurate coagulation testing, making them unsuitable choices for this specific test.