American Medical Technologist (AMT) Practice Exam

When serum is left on a blood clot for an extended period, such as over an hour, the serum glucose levels decrease. This occurs because glucose is utilized by cells in the clot and possibly by white blood cells that remain active even after the blood has clotted. These cells continue to metabolize glucose, which can lead to a decrease in the concentration of glucose found in the serum.

The other options can be examined in context: serum does not typically become contaminated just from being left on a clot for a short while; contamination is more related to improper handling or exposure. Serum protein levels do not increase in this scenario; they remain relatively unchanged unless there is an active process that alters protein synthesis or degradation. Lastly, serum stability implies that there should be no significant alterations in its composition, which is not the case here, particularly with glucose levels. Therefore, monitoring the glucose level is crucial when serum is not promptly separated from the clot.