CSMLS Exam 2025 – 400 Free Practice Questions to Pass the Exam

The correct answer indicates that a red stoppered evacuated tube typically does not contain any additive. This type of tube is primarily designed for serum collection, allowing the blood to clot naturally before the serum is separated by centrifugation. When blood is collected in a tube without additives, it results in serum that is free from anticoagulants or other substances that may interfere with the tests performed on the serum.

In contrast, tubes with additives such as EDTA, SPS, or sodium heparin serve specific purposes. EDTA is commonly found in purple stoppered tubes and is used for hematology tests because it prevents coagulation. SPS is an additive in yellow stoppered tubes and is mainly used for blood cultures to inhibit the activity of certain antibiotics, while sodium heparin, contained in green stoppered tubes, is an anticoagulant used for various chemistry tests requiring plasma. Therefore, recognizing the characteristics and uses of different tube types and their additives is essential for proper sample collection and testing in a laboratory setting.