Which statement is incorrect regarding centrifuge operation?

• A. Remove evacuated tube stoppers before placing them in the centrifuge.
• B. Centrifuge serum specimens before they start to form noticeable clots.
• C. Place tubes of equal size and volume opposite one another for balance.
• D. Never centrifuge both serum and plasma specimens in the same centrifuge.

Answer: (A)

Stoppers stay on during centrifugation because the high-speed rotation can push liquid out of uncapped tubes and create aerosols or spills, posing a contamination and exposure risk to staff and equipment. Keeping the caps in place helps contain the sample and maintain sample integrity. The other points describe correct centrifuge handling: load tubes of equal size and volume opposite each other to keep the rotor balanced and prevent damage, and follow the appropriate timing for serum vs. plasma separation so you obtain a clean, well-separated specimen. In practice, whether you spin different specimen types in the same run depends on lab protocol and proper balancing, but removing stoppers beforehand is universally unsafe.