American Medical Certification Association (AMCA) Phlebotomy Practice Exam 2025 - Free Phlebotomy Practice Questions and Study Guide

The light blue-top tube, which contains sodium citrate, is specifically designed for coagulation testing. This tube type plays a vital role in preserving the functionality of clotting factors in blood samples, which is essential for accurate coagulation results. The sodium citrate acts as an anticoagulant by chelating calcium ions necessary for the coagulation process, thereby preventing the blood from clotting in the tube. This allows healthcare professionals to assess the patient's coagulation status through tests such as prothrombin time (PT) and activated partial thromboplastin time (aPTT), crucial in diagnosing bleeding disorders or monitoring anticoagulation therapy.

In contrast, other tube types do not contain the appropriate anticoagulant for coagulation tests and would either lead to clotting of the sample or interfere with the testing process. Therefore, the use of the light blue-top tube is critical for ensuring reliable and valid results in coagulation studies.