Lab Test

Alkaline Phosphatase Isoenzymes

Alkaline Phosphatase Fractionation, Fractionated Alkaline Phosphatase, Alk Phos

Test Codes

Antrim #17265, Antrim #17300, EPIC: LAB5006, EPIC: LAB5846, SOFT: ALP, SOFT: APISO


Special Chemistry

Specimen Collection Criteria

Collect: One Gold-top SST. (Minimum Whole Blood: 2.0 mL)

See Minimum Pediatric Specimen Requirements for Microtainer® collection.

Specimen should be collected at least 2 hours post prandially to avoid transient increases in intestinal alkaline phosphatase.

Physician Office/Draw Specimen Preparation

Let SST specimens clot 30-60 minutes then immediately centrifuge to separate serum from cells. Refrigerate (2-8°C or 36-46°F) the centrifuged SST tube within two hours of collection. (Minimum Serum: 0.5 mL)

Preparation for Courier Transport

Transport: Centrifuged SST tube, refrigerated (2-8°C or 36-46°F). (Minimum Serum: 0.5 mL)

Rejection Criteria

  • Plasma specimens. 
  • Grossly hemolyzed, lipemic or icteric specimens. 
  • Red-top tubes with serum not separated from cells within two hours of collection.
  • Specimens with total Alkaline Phosphatase levels lower than 111 U/L.

In-Lab Processing

Let SST specimens clot 30-60 minutes. Centrifuge SST tubes or Microtainers® to separate serum from cells. Deliver immediately to the appropriate testing station. (Minimum Serum: 0.5 mL)


Specimen Stability for Testing:

Centrifuged SST Tubes and Microtainers® with Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): Unacceptable

Red-top Tubes and Microtainers® without Separator Gel
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Serum Specimens (Pour-Overs)
Room Temperature (20-26°C or 68-78.8°F): 2 hours
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 14 days

Specimen Storage in Department Prior to Disposal:

Refrigerated (2-8°C or 36-46°F): 7 days


Royal Oak Special Testing Laboratory


3 times a week, afternoons.
Routine results available within 7 days.

Reference Range

Adult male & female:

Total Alkaline Phosphatase: 30-110 U/L.
Total Liver Fraction (Includes Liver 2): 25-74 U/L.
Liver 2 Fraction: 2-17 U/L.
Bone Fraction: 9-44 U/L.
Intestinal Fraction: 1-11 U/L.

Alkaline Phosphatase (ALP)

Test Methodology

Separation by Agarose Gel Electrophoresis.


Increased liver alkaline phosphatase is seen in obstructive liver disease (cholestasis). Evidence of high molecular weight liver complexes is also consistent with cholestasis.

Bone alkaline phosphatase will be increased in any conditions producing osteoblastic activity including physiologic bone growth in children and adolescents, healing fractures, Paget's disease, osteoporosis or osteomalacia, rickets, osteosarcoma of bone and others.

Intestinal alkaline phosphatase may be increased due to a recent fatty meal, in intestinal diseases, and in patients with blood types O and B who are secretors.

Obstruction may be present at any level from intrahepatic ducts (as in primary biliary cirrhosis or space-occupying lesions) to the common bile duct. Because hepatocellular damage and cholestasis often occur together, but with one predominating, liver alkaline phosphatase is commonly increased (slightly) in viral hepatitis.

Atypical alkaline phosphatases are occasionally seen and may be due to immunoglobulin-binding. The clinical significance is unknown. 

Atypical alkaline phosphatase isoenzyme patterns may occur due to immunoglobulin-binding, which retards enzyme removal from the circulation.  Immunoglobulin binding to enzymes has not been shown to be clinically relevant and is not generally associated with disease.

Rarely, other atypical isoenzymes may be present which are difficult to identify and may interfere with quantitation of liver, bone, and intestinal isoenzyme fractions. 

Clinical Utility

This assay is used to differentiate between liver, bone and intestinal isoenzymes in patients with an elevated serum alkaline phosphatase.

CPT Codes

84075, 84080.
LOINC:  6768-6


Last Updated


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