Serum alkaline phosphatase is a measure of osteoblastic activity, which is increased in Paget's disease of bone. Effective therapy with bisphosphonates or other drugs causes a reduction in alkaline phosphatase activity.
NOTE: The articles do not specify the use of bone-specific alkaline phosphatase. For an older adult with no other disease the total activity would be accurate enough and more readily accessible. In the presence of hepatobiliary disease or tumor then the bone-specific isoenzyme may need to be measured.
percent decrease in alkaline phosphatase activity =
significant decrease lasting >= 2 months without treatment
remission
persistent > 25% increase from nadir
relapse
where:
• A negative decrease is an increase.
• Some people use an average of multiple readings to determine baseline and nadir.
• Some people recognize a complete response ("normalized") if the person's alkaline phosphatase returns to the normal range, but others note that people with a dramatic decrease in enzyme activity may not achieve a normal value.
Limitations:
• A person should be monitored using the same assay with results reported in the same units.
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