Type of test : Blood

Normal findings

 Adult: 30-120 units/L or 0.5-2.0 μKat/L

 Elderly: slightly higher than adults

 Child/adolescent: < 2 years: 85-235 units/L        2-8 years: 65-210 units/L

 9-15 years: 60-300 units/L                                   16-21 years: 30-200 units/L

Test explanation and related physiology Although ALP is found in many tissues, the highest concentrations are found in the liver, biliary tract epithelium, and bone. Detection of this enzyme is important for determining liver and bone disorders. Enzyme levels of ALP are greatly increased in both extrahepatic and intrahepatic obstructive biliary disease and cirrhosis. Reports have indicated that the most sensitive test to indicate metastatic tumor to the liver is ALP.

Bone is the most frequent extrahepatic source of ALP; new bone growth is associated with elevated ALP levels, which explains why ALP levels are high in adolescents. Pathologic new bone growth occurs with osteoblastic metastatic (e.g., breast, prostate) tumors. Paget disease, healing fractures, rheumatoid arthritis, hyperparathyroidism, and normal-growing bones are sources of elevated ALP levels as well.

Isoenzymes of ALP are sometimes used to distinguish between liver and bone diseases. The detection of isoenzymes can help differentiate the source of the pathology associated with the elevated total ALP. ALP1 is from the liver. ALP2 is from the bone.

Interfering factors

• Recent ingestion of a meal can increase ALP levels.

* Drugs that may cause elevated ALP levels include albumin made from placental tissue, allopurinol, antibiotics, azathioprine, colchicine, fluorides, indomethacin, isoniazid (INH), methotrexate, methyldopa, nicotinic acid, phenothiazine, probenecid, tetracyclines, and verapamil.

*  Drugs that may cause decreased levels include arsenicals, cyanides, fluorides, nitrofurantoin, oxalates, and zinc salts.

Procedure and patient care

 • See inside front cover for Routine Blood Testing.

 • Fasting: no

• Blood tube commonly used: red

 • Note that overnight fasting may be required for isoenzymes.

• Patients with liver dysfunction often have prolonged clotting times.

Abnormal findings

 Increased levels

- Cirrhosis

- Intrahepatic or extrahepatic biliary obstruction

- Primary or metastatic liver tumor

- Intestinal ischemia or infarction

- Metastatic tumor to the bone

- Healing fracture

- Hyperparathyroidism

- Paget disease of bone

- Rheumatoid arthritis

- Sarcoidosis

- Osteomalacia

- Rickets

Decreased levels

- Hypothyroidism

- Malnutrition

- Milk-alkali syndrome

- Pernicious anemia

- Hypophosphatemia

- Scurvy (vitamin C deficiency)

- Celiac disease

- Excess vitamin B ingestion

- Hypophosphatasia