Which of the following is NOT a laboratory test performed on royal blue tubes?

• A. Toxicology
• B. Hematology
• C. Trace elements
• D. Natural chemistry test

Answer: (B)

Royal blue tubes are specifically used when metal-free sample handling is required, such as for trace elements and toxicology testing. These tests need to minimize contamination from metals in the tube itself, which is why royal blue tubes are designed with minimal or no metal additives and specialized interiors. Hematology, on the other hand, analyzes blood cells and requires an anticoagulant like EDTA to preserve cells, which is provided by purple (EDTA) tubes rather than royal blue tubes. Because of this anticoagulant requirement and the tube design, hematology tests are not performed on royal blue tubes. The other options align with royal blue tube usage for trace elements and toxicology.