Which type of tube is required to be filled completely?

The light blue tube is specifically designed for coagulation studies and requires complete filling to ensure accurate test results. This type of tube contains sodium citrate, which functions as an anticoagulant by binding calcium in the blood. When performing coagulation tests, the ratio of blood to anticoagulant is critical, and filling the tube completely ensures that this ratio remains consistent for every sample. Inadequate filling could lead to insufficient anticoagulant being present, resulting in erroneous test outcomes, which could misguide clinical decisions.

The need for complete filling in light blue tubes stems from the nature of the tests conducted with them, such as PT (Prothrombin Time) and aPTT (Activated Partial Thromboplastin Time). Accuracy in these measurements is vital for diagnosing clotting disorders or monitoring anticoagulant therapy. Hence, the requirement that the light blue tube be filled completely is paramount for valid test results.