Alkaline Phosphatase (ALP)
Test Description
Alkaline phosphatase (ALP) is an enzyme found in the liver, bone, placenta, intestine,
and kidneys but primarily in the cells lining the biliary tract and in the
osteoblasts involved in the formation of new bone. ALP is normally excreted from
the liver in the bile. Increased ALP levels are found most commonly during periods
of bone growth (as in children), in various types of liver disease, and in biliary
obstruction. ALP is also considered a tumor marker that increases in the case of
osteogenic sarcoma and in breast or prostate cancer that has metastasized to the
bone.
Normal Values
Female: 30–100 U/L (0.5–1.67 mkat/L SI units)
Male: 45–115 U/L (0.75–1.92 mkat/L SI units)
Elderly: Slightly higher norms
Children: One to three times adult norms
Puberty: Five to six times adult norms
Possible Meanings of Abnormal Values
Increased Decreased
Biliary obstruction Celiac disease
Bone metastases Chronic nephritis
Calcium deficiency Cystic fibrosis
Cancer of head of pancreas Excessive vitamin D intake
Cirrhosis Genetic defect
Eclampsia Hypophosphatemia
Healing fracture Hypothyroidism
Hepatitis Lack of normal bone formation
High-fat intake Malnutrition
Hyperparathyroidism Milk-alkali syndrome
Infectious mononucleosis Pernicious anemia
Leukemia Placental insufficiency
Liver cancer Scurvy
Osteogenic sarcoma
Osteomalacia
Paget’s disease
Pancreatitis
Pregnancy
Rheumatoid arthritis
Rickets
Vitamin D deficiency
Contributing Factors to Abnormal Values
• Hemolysis of the blood sample may alter test results.
• Drugs that may increase ALP levels are numerous and include: ACE-inhibitors,
acetaminophen, anticonvulsants, antibiotics, antipsychotics, benzodiazepines,
estrogens, ferrous sulfate, heparin, interferons, lipid-lowering agents, NSAIDs, salicylates,
thiazides, trimethobenzamide, variconazole.
• Drugs that may decrease ALP levels: arsenicals, cyanides, fluorides, nitrofurantoin,
oxalates, phosphates, propranolol, zinc salts.
Interventions/Implications
Pretest
• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.
• Fasting for 10 to 12 hours is usually required before the test.
Procedure
• A 7-mL blood sample is drawn in a red-top collection tube.
• Gloves are worn throughout the procedure.
Post test
• Apply pressure 3 to 5 minutes at venipuncture site. Apply dressing, periodically assessing
for continued bleeding.
• Teach the patient to monitor the site. If the site begins to bleed, the patient should apply
direct pressure and, if unable to control the bleeding, return to the laboratory or notify
the primary care provider.
• Label the specimen and transport it to the laboratory.
• Report abnormal findings to the primary care provider.
Clinical Alerts
• With liver dysfunction, patient may have prolonged clotting time.
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