Prolonged exposure of serum to the blood cells before the serum is removed from the clot can result in:

• A. Increased serum glucose
• B. Increased serum phosphorus
• C. Increased serum enzyme activity
• D. Increased serum sodium

Answer: (B)

When serum is left in contact with the clot and cells for too long, the cells can release intracellular contents into the serum. Phosphate is abundant inside cells, so any cell damage or leakage during this extended contact causes inorganic phosphate to enter the serum, raising its measured level. This is why prolonged exposure tends to increase serum phosphorus. In contrast, glucose would usually decrease because cells continue to metabolize it, and sodium isn’t typically elevated by this artifact; enzyme activity could rise if enzymes leak from cells, but the most consistent, expected change with this handling is a higher serum phosphorus.