A blood specimen collected in a nongel tube has been centrifuged. The term used to describe the liquid portion on top of the cells is what?

The correct term to describe the liquid portion on top of the cells in a blood specimen collected in a nongel tube after centrifugation is serum. Serum is the fluid that remains after the blood has clotted and the clot has been removed, which is typically what happens with red-top or gold-top tubes that do not contain any anticoagulant.

In this case, the function of a nongel tube is to allow for the collection of serum upon separation from the cellular components after centrifugation. The other terms are not applicable in this scenario. Plasma, for instance, refers to the liquid portion of blood that is obtained when the blood is prevented from clotting by an anticoagulant, which is not the case with a nongel tube. Semen is a completely different bodily fluid associated with reproduction, containing sperm and fluids from various glands. Interstitial fluid is found in the spaces between cells, not in the blood collection process.

Therefore, the definition and the context of serum make it the correct answer for the liquid portion found in this case.