If there is only a small amount of serum separated after centrifuging a tube of whole blood and you need more for testing, what should you do?

If there is only a small amount of serum separated after centrifuging a tube of whole blood and you need more for testing, what should you do?

• A. Invert the tube several times and respin it
• B. Rim/ring the clot and spin again at a normal speed and time
• C. Spin the tube again at a faster speed and a longer time
• D. Assume the patient is dehydrated and draw off all of the serum you can

Answer: (B)

When serum needs to be maximized, the goal is to free any serum that may be trapped in or around the clot and then re-separate it from the clot. Carefully rim or loosen the clot at the top so that the remaining serum can be released, then spin again at the normal speed and time. This approach pulls more serum into the liquid layer without disturbing the sample or causing damage. Simply inverting the tube after the initial spin risks resuspending the clot and doesn’t increase usable serum. Spinning faster or for a longer time can cause hemolysis or other artifacts and isn’t the correct way to obtain more serum. Dehydration status isn’t something you can reliably infer to obtain more serum from the same tube.

When serum needs to be maximized, the goal is to free any serum that may be trapped in or around the clot and then re-separate it from the clot. Carefully rim or loosen the clot at the top so that the remaining serum can be released, then spin again at the normal speed and time. This approach pulls more serum into the liquid layer without disturbing the sample or causing damage. Simply inverting the tube after the initial spin risks resuspending the clot and doesn’t increase usable serum. Spinning faster or for a longer time can cause hemolysis or other artifacts and isn’t the correct way to obtain more serum. Dehydration status isn’t something you can reliably infer to obtain more serum from the same tube.