Alkaline Phosphatase Isoenzymes (Blood)

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Alkaline Phosphatase Isoenzymes (Blood)

Testing Laboratory

Auckland Te Toka Tumai | Auckland Hospital

Department

Chemical Pathology

Delphic Registration Code (Alpha Code)

ALPI

Test Code (Numeric Code)

7121

Laboratory Handling

Phlebotomy

Serum

Transport

Ambient

Laboratory

LabPlus Immunochemistry

Test Adds Requirement

Samples are stored at -20°C for 1 month

Sample Stability

2 - 8°C for 1 week; -20°C for at least 14 days

Associated Tests

Alkaline Phosphatase (Blood)

Synonyms

ALPI
ALP isoenzymes
Alkaline phosphatase electrophoresis
ALP electrophoresis
Bone ALP
Placental ALP
Intestinal ALP
Hepatic ALP
MacroALP
Macro ALP

Turnaround Time

2 weeks

This test may be vetted by the laboratory. Please include relevant clinical information on the request form to ensure appropriate tests are approved. See the 'Clinical Information' section below for more information on the indications for testing.

Specimen Type

Serum

Specimen Requirements

Tube/Container Type:

Preferred

SST II (Gold Cap)

Acceptable

Plain (Red Top)

Preferred Sample Volume (ml)

Minimum Sample Volume (ml)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Plain(Microtainer)

Preferred Sample Volume (ml)

0.5

Minimum Sample Volume (ml)

0.25

Pre-testing Requirements

Samples with a total alkaline phosphatase less than 2x the upper limit of the reference interval may not be tested for alkaline phosphatase isoenzymes as analysis may be unhelpful in this situation.

Additional Specimen Information

To assist in the reporting of ALP isoenzymes full clinical details and recent LFT, ALP and P1NP results must accompany the request . If LFT and P1NP results are not provided LabPLUS will perform these tests before completing ALP isoenzyme analysis.

Diagnostic Use

The test differentiates the various forms (and thus sources) of ALP to determine why ALP may be elevated.

The test may not be necessary when there is already a clear source for ALP, such as:

Pregnancy – Placental and bone ALP.
Signs and symptoms specific to bone (e.g. skeletal pain, elevated P1NP) or liver (e.g. jaundice, elevated GGT).

ALP isoenzyme determination is most likely to be helpful with sustained increase (>6 months) in total ALP when liver and bone markers are normal, and no cause for the increase is apparent clinically.

Interpretation

CAUSES OF ISOLATED ALP ELEVATION
Benign familial hyperphosphatasemia is a cause for an unexplained isolated increased ALP and is seen at any age. Typically, the intestinal isoenzyme is increased, with or without increased bone or liver isoenzyme as well. This is an asymptomatic genetic variant; all other liver enzymes are normal, and there is no evidence for increased bone turnover (normal P1NP). Other family members may also have a raised ALP.

In transient hyperphosphatasemia of infancy, the ALP level may be very high (thousands) and typically persists for a few months. The pathogenesis is not known, but it has been suggested to follow viral infections.

Apart from liver and bone, this test may identify other ALP isoenzymes:

a. Placental type – from pregnancy or Regan isoenzymes from tumors (e.g. pancreas, ovary, lung, breast)

b. Placental-like ALP type – from smoking or germ cell tumors e.g. from testis, thymus, lung

c. ‘Fast liver’ type – seen in transient hyperphosphatasemia of infancy

d. ‘Atypical bone’ type – from raised neutrophils in some patients with e.g. polycythaemia rubra vera, chronic neutrophilic leukaemia, malignant lymphoma, lung cancer

e. Intestinal type – may be benign (e.g. related to a recent fatty meal, some families have detectable intestinal ALP), or related to liver cirrhosis, colitis or some tumours

f. Stauffer’s syndrome e.g. in renal cell cancer (predominantly liver isoenzyme)

This test does not have the sensitivity to detect CSF placental ALP for the diagnosis of primary intracranial germinomas.

Only in very selected cases with equivocal presence of placental isoenzyme on electrophoresis or suspected low activity placental isoenzyme, the Placental Alkaline Phosphatase Test (heat denaturation) may provide additional information:

5 mL blood either in plain or heparin tube (minimum of 0.5 mL of serum or plasma) is required
Result is usually available within 3 hours, but not outside 0800-1700 weekdays
If the remaining ALP activity after heat denaturation is close to 90-100%, it is suggestive of placental or Regan isoenzyme

Reference Intervals

Qualitative interpretation

Test Method

Electrophoresis (Sebia kit)

Limitations / Interference

Hemolysed samples cannot be accepted. Samples collected in EDTA, Citrate or Oxalate tubes cannot be accepted as they contain an inhibitor to alkaline phosphatase enzymatic activity.

The test is qualitative, based on the intensity of staining, and thus the cause of a mild elevation in ALP may be impossible to determine.

Uncertainty of Measurement

N/A, qualitative test

Last updated: 13/05/2026

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Overview

Testing Laboratory

Department

Delphic Registration Code (Alpha Code)

Test Code (Numeric Code)

Laboratory Handling

Phlebotomy

Transport

Laboratory

Test Adds Requirement

Sample Stability

Associated Tests

Synonyms

Turnaround Time

Specimen

Specimen Type

Specimen Requirements

Tube/Container Type:

Preferred

Acceptable

Preferred Sample Volume (ml)

Minimum Sample Volume (ml)

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

Preferred Sample Volume (ml)

Minimum Sample Volume (ml)

Pre-testing Requirements

Additional Specimen Information

Referral

Aliquot Instructions

Sample Type

Minimum Volume (ml)

Transport to Lab

Additional Referral/Aliquot Information

Clinical Information/Test Method

Diagnostic Use

Interpretation

Reference Intervals

Test Method

Limitations / Interference

Uncertainty of Measurement

Additional Information

Resources

Contact Information

Contact Information

Enquiry Form

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