What Is an Alkaline
Phosphatase Bone Isoenzyme Test?
Alkaline phosphatase (ALP) is an enzyme naturally present
throughout your body. It comes in many variations called isoenzymes. Each
isoenzyme of ALP is different, depending on where in your body it’s made.
Your bones make an isoenzyme called ALP-2. Levels of this enzyme
increase when bones are growing or bone cells are active.
An ALP bone isoenzyme test can detect abnormal levels of bone
growth that may be associated with conditions such as:
- Paget’s disease of bone
- certain bone cancers
Other names for an ALP bone isoenzyme test include:
- an ALP-2 test
- bone-specific alkaline phosphatase test
- bone-specific ALP test
What Is the Purpose of this
Doctors order an ALP-2 test if they’re concerned you may have a
The symptoms of bone disease include:
- chronic bone and joint pain
- bones that are brittle or break easily
- deformed bones
An ALP-2 test can also be used to monitor bone disease
What Do I Need to Do to Get
Ready for the Test?
Your doctor may tell you not to eat or drink anything for six to
12 hours before the test. You may be asked to stop certain medications before
the test. Follow your doctor’s orders carefully. Your test results could be
incorrect if you don’t.
Certain drugs may affect ALP-2 levels. These include:
- birth control pills
It’s important to tell your doctor about all the medicines
you’re taking. This includes both prescription and over-the-counter drugs.
How Does the Test Work?
The ALP bone isoenzyme test is a blood test.
A nurse or laboratory technician will draw your blood.
A tourniquet will be tied around your upper arm. A vein will be
located for the blood draw. The area around it will be cleaned. A needle will
be inserted, and blood will be drawn into a small vial. You may feel a slight
pinch. Your blood will be sent to a lab for diagnosis.
Sometimes, blood may be taken from a vein on the back of your
hand instead of from one inside your elbow.
Interpreting Test Results
The ALP bone isoenzyme range for healthy adults is 12.1 to 42.7.
Children have higher levels of ALP bone isoenzyme. ALP-2 is also
elevated in people with broken bones. In both groups, bone growth is expected
Higher than normal levels of ALP bone isoenzyme could indicate a
bone disease such as:
- osteoblastic bone tumors
- osteomalacia, or rickets
- Paget’s disease
An elevated test result could also indicate serious conditions
such as hyperparathyroidism or leukemia. Both diseases affect your bones as
well as other parts of your body.
Test results below normal are sometimes found in people with malnutrition
or anemia. Results that are below normal can also be found in women who take
estrogen after menopause. However, high levels are much more common than low
Follow-Up After the Test
The ALP bone isoenzyme test isn’t used to diagnose a disease on
its own. It can only narrow down the list of causes for your symptoms.
If you have a positive test, further tests will probably be
necessary. These tests will determine what type of bone disease you may have.