Alkaline Phosphatase (ALKP)

CPT Code: 84075
Specimen: Serum or Plasma
Volume: 2 mL
Minimum Volume: 0.5 mL
Container: Red-top tube, gel-barrier tube, or green-top (heparin) tube
Methodology: Kinetic
Collection: If a red-top tube or green-top tube is used, transfer separated serum or plasma to a plastic transport tube.  Separate serum or plasma from cells within 45 minutes of collection.  Complete clot formation should take place before centrifugation.
Reference Range: 50-136 IU/L

Stability:  

Temperatures Period
Room Temperature 8 Hours
Refrigerated (2-8 ⁰C)7 Days
Frozen (-20 ⁰C)6 Months

 

Use: Measurements of alkaline phosphatase are used in the investigation of hepatobiliary and bone disease, usually producing elevated results.  Although this enzyme is found in all body tissue, the primary sites in adults are bone and liver with a small amount in the intestine.

Clinical

Significance:

High ALP causes may include bone growth, healing fracture, acromegaly, osteogenic sarcoma, liver or bone metastases, hypervitaminosis D, paget disease, leukemia, myelofibrosis, and rarely myeloma.

Other causes may include hyperthyroidism, hyperparathyroidism, chronic alcohol ingestion, biliary obstruction, cirrhosis, gilbert syndrome, hepatitis, fatty metamorphosis of liver, diabetes mellitus, diabetic hepatic lipidosis, sepsis, certain viral diseases postoperative cholestasis, pancreatitis, carcinoma of pancreas, cystic fibrosis, pulmonary infarct, tumors, fanconi syndrome peptic ulcer, erosion, and congestive heart failure.

Drugs − estrogens (large doses), birth control agents, methyltestosterone, phenothiazines, oral hypoglycemic agents, erythromycin, or any drug producing hypersensitivity or toxic cholestasis.

Levels of alkaline phosphatase in children (due to increased bone growth), pregnant women, and older patients are normally higher.

Low ALP causes include: Hypothyroidism, pernicious anemia, and hypophosphatasia. 

Malnutrition has been reported to relate to low values, but in practice, diseases causing malnutrition relate often to high alkaline phosphatase results (eg, disseminated neoplasia).

Some drugs such as clofibrate, azathioprine, estrogens and estrogens in combination with androgens.

Causes for

Rejection:

Hemolysis; plasma specimen; specimen collected in EDTA tube; improper labeling.
Interfering Substances:

Bilirubin (unconjugated) of 60 mg/dL increases an ALP result of 188 U/L by 14%.

EDTA when present at 200mg/dL depresses the ALP results by 80 U/L of alkaline phosphate activity.

Tryglycerides (endogenous) of 3000 mg/dL depresses an ALP result of 162 U/L by 13%.