Monitoring Response to Therapy for Paget's Disease Using Serum Alkaline Phosphatase

 

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 =

= ((previous value) - (current value)) / (previous value) * 100%

Percent Change	Diagnosis
> 25% decrease	response
no change to therapy to <= 25% decrease	nonresponder (resistant)
increase from baseline during therapy	progression
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.