Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which analyte is increased when serum is left sitting on a clot?

1. Glucose

2. Protein

3. Albumin

4. Potassium

The correct answer is: Potassium

When serum is left sitting on a clot, the analyte that is typically increased is potassium. This happens due to the release of potassium ions from red blood cells that break down during the clotting process. As the cells lyse, they release intracellular contents, including potassium, into the serum. This can lead to a false elevation in potassium levels if the serum is not separated from the clot promptly. The other analytes listed would not show this behavior. For instance, glucose levels may decrease rather than increase due to glycolysis, a metabolic process that continues after blood collection, leading to the consumption of glucose by the remaining red blood cells. Protein levels, including albumin, generally remain stable and do not significantly increase just from the serum being left on a clot, as they are more influenced by other factors, such as hydration status and liver function.