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Alkaline phosphatase isoenzymes

Test performed by: LabPLUS VIM Proteins

This test may be vetted by a pathologist.

The clinical information for the test must be clearly written on the request form. If clinical information is not provided, or does not provide sufficient justification for the test, the test may be declined.

Declined tests :

If a test is declined, the specimen will be held for a reasonable period (usually 3 weeks but dependant on the stability of the sample). Medical practitioners seeking approval for a declined test should email the on-call Chemical Pathologist ( chemicalpathologist@adhb.govt.nz ) , giving the patient's name and NHI number and the clinical justification for the test. If unable to email, call the on-call Chemical Pathologist via Lablink (09-3078995) and identify yourself as a doctor.  

Test vetting policy

Specimen Collection
SST3.5 mL SST Serum (Preferred)
Plain4 mL Adult Plain Serum
Plain500 uL Paediatric Plain Serum

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

Reference Intervals

The alkaline phosphatase isoenzymes are separated by electrophoresis into different bands. The relative position and colour intensity of the bands with and without lectin ( a migration retarding sugar-binding protein ) can provide a qualitative impression as to the organ origin of the alkaline phosphatase isoenzyme(s).    

Uncertainty of Measurement:    Not applicable: a qualitative test with report comment 

Turnaround Time: Within 2 weeks
Diagnostic Use and Interpretation

Requests for ALP isoenzymes will be vetted by Labplus chemical pathologists taking account of the following considerations:

If ALP is less than 2x the upper limit of the age-related range, ALP isoenzyme determination is rarely helpful in determining the cause. Transient non specific increases are common during acute illness in adults and children and often return to normal within a few months.

When other liver enzymes are normal P1NP may be a more helpful marker than ALP isoenzymes for detection of bone disease.

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. If you wish to discuss the value of this investigation please contact one of the chemical pathologists vie email   chemicalpathologist@adhb.govt.nz

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.


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 hyperphosphatasaemia 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 tumours (e.g. pancreas, ovary, lung, breast)

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

c.        'Fast liver'  type - seen in transient hyperphosphatasaemia 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 - from liver cirrhosis or colitis or tumour eg. hepatoma

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


1. Rosalki SB, Foo AY, Dooley JS. Benign familial hyperphosphatasaemia as a cause of unexplained increase in plasma alkaline phosphatase activity. J Clin Pathol. 1993;46:738-741

2. Stein, P., S. B. Rosalki, et al. (1987). "Transient hyperphosphatasemia of infancy and early childhood: clinical and biochemical features of 21 cases and literature review." Clin Chem 33(2 Pt 1): 313-318.

Alkaline phosphatase

Placental Alkaline Phosphatase

Contact Information

Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.

If the query concerns a specific patient please include the NHI number in your email.

If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).

Individual chemical pathologists may be contacted but will not be available at all times.

Dr Cam Kyle (Clinical Head): CampbellK@adhb.govt.nz   ext 22052 or mobile 027 276 0038

Dr Carol Siu: CarolSiu@adhb.govt.nz  ext. 22574 or mobile 027 536 0299

Dr Weldon Chiu: WeldonC@adhb.govt.nz   ext. 23427 or mobile 027 290 1073 

Dr Leah Ha: LHa@adhb.govt.nz  ext. 23427 or mobile 021 308 806  

Dr Samarina Musaad: SamarinaM@adhb.govt.nz ext. 22402 or mobile 021 404 769

Dr Campbell Heron (Registrar): CHeron@adhb.govt.nz  ext. 22030 or mobile 027 772 2895

Last updated at 10:43:25 04/02/2020