When serum is heated to 56 degrees Celsius for 10 minutes, it is primarily done to distinguish between different types of alkaline phosphatase (ALP) based on their thermal stability.
Bone specific ALP is less heat-stable compared to other isoenzymes like liver or placental ALP. Specifically, when bone ALP is present, it is expected that a certain percentage of this enzyme will remain active after being subjected to this heat treatment. The correct interpretation of the activity levels after heating plays a key role in identifying the isoenzyme in question.
In the context of this scenario, if less than 20% of the activity remains, it signifies that a significant portion of the enzyme has been denatured, which is characteristic of heat-sensitive bone ALP. Therefore, the choice that indicates less than 20% activity remaining is indicative of the presence of bone ALP in the serum being tested.
This outcome allows clinicians and laboratory technologists to infer that bone ALP is present due to the thermal sensitivity observed in the results following the heating process. The other options do not adequately reflect the expected activity levels associated with the presence of bone ALP, making them incorrect in this assessment.