MedlinePlus Medical Encyclopedia: ALP (alkaline phosphatase) isoenzyme

Skip navigation


Medical Encyclopedia
Other encyclopedia topics:	A-Ag Ah-Ap Aq-Az B-Bk Bl-Bz C-Cg Ch-Co Cp-Cz D-Di Dj-Dz E-Ep Eq-Ez F G H-Hf Hg-Hz I-In Io-Iz J K L-Ln Lo-Lz M-Mf Mg-Mz N O P-Pl Pm-Pz Q R S-Sh Si-Sp Sq-Sz T-Tn To-Tz U V W X Y Z 0-9

ALP (alkaline phosphatase) isoenzyme

Contents of this page:
Illustrations Definition How the test is performed How to prepare for the test How the test will feel	Why the test is performed Normal Values What abnormal results mean What the risks are Special considerations

Illustrations

Blood test

Definition Return to top

A blood test to measure the amounts of different forms of alkaline phosphatase.

Alkaline phosphatase is an enzyme in the blood, intestines, liver, and bone cells. Its chemical structure varies (called isoenzymes) depending on where it is produced. This makes it possible to determine where a problem has originated. When bones are growing, liver cells are damaged, or a biliary obstruction occurs, alkaline phosphatase levels rise considerably.

How the test is performed Return to top

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For an infant or young child:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test Return to top

Fasting for 10 to 12 hours before the test is usually standard. A urine specimen may also be tested (your health care provider determines which tests are appropriate). Many drugs affect the level of alkaline phosphatase in the blood. These drugs will be monitored or you will be instructed to discontinue their use:

antibiotics
narcotics
methyldopa
propranolol
cortisone
allopurinol
tricyclic antidepressants
chlorpromazine
estrogens and progestins - oral contraceptives
anti-inflammatory analgesics - oral
male hormones
tranquilizers
some antiarthritic drugs
antidiabetics - oral

For infants and children:
The preparation you can provide for this test depends on your child's age and previous experience. For specific information regarding how you can prepare your child, see the following topics:

infant test or procedure preparation (birth to 1 year)
toddler test or procedure preparation (1 to 3 years)
preschooler test or procedure preparation (3 to 6 years)
schoolage test or procedure preparation (6 to 12 years)
adolescent test or procedure preparation (12 to 18 years)

How the test will feel Return to top

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed Return to top

This test is useful in diagnosing:

liver disease (jaundice-yellowing of the skin and eyes)
the cause of liver disease
parathyroid disease
Vitamin D deficiency
the cause of pain in the upper abdomen
bone diseases

It can also be used to monitor:

patients on medications that may be harmful to the liver
liver production (used in conjunction with other tests)

Normal Values Return to top

The normal value is 20 to 140 IU/L (international units per liter)

Adults have lower levels of ALP than children because children's bones are still growing. During some growth spurts, levels can be as high as 500 IU/L. Usually children are not measured because of the potential for such high amounts, so the abnormal results refer to adults.

The isoenzymes can reveal whether the increase is in "bone" ALP or "liver" ALP.

What abnormal results mean Return to top

Higher-than-normal ALP levels may indicate:

pregnancy
healing bone fracture
liver diseases
biliary obstruction
hepatitis
bone disease
Paget's disease
osteoblastic bone cancers
osteomalacia
rickets
skeletal disease
anemia
rickets
leukemia
thyroid gland infection
hyperparathyroidism
chronic alcohol ingestion

Lower-than-normal levels of ALP may indicate:

protein deficiency
magnesium deficiency
too much vitamin D or too little vitamin C
poor nutrition

What the risks are Return to top

excessive bleeding
fainting or feeling light-headed
hematoma (blood accumulating under the skin)
infection (a slight risk any time the skin is broken)
multiple punctures to locate veins

Special considerations Return to top

This test is about 80% accurate for identifying specific locations of cancers or disease. It should not be relied on for a screening test because sometimes levels are high for unknown reasons and return to normal. Unless there is evidence of a disease, higher-than-normal values of alkaline phosphatase in the Chem-20 test are not considered significant.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Update Date: 8/18/2003

Updated by: David Webner, M.D., Sports Medicine Fellow, Crozer-Keystone Family Practice Program, Springfield, PA. Review provided by VeriMed Healthcare Network.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2002 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.