Pathology Handbook

Alkaline Phosphatase Isoenzymes


ALP isoenzymes

Clinical Indications

1) Investigation of suspected transient hyperphosphatasaemia of childhood. This may occur in some younger adults. 

2) In other patients, isoenzyme analysis may, rarely, be useful to investigate the origin of an unexplained elevated alkaline phosphatase level.

3) Abnormalities in liver function tests may occur during normal pregnancy (probably due to increased level of oestrogens) and levels of gamma-GT and alkaline phosphatase (ALP) rise in late pregnancy; the latter mainly due to placental (heat-stable) ALP. The most pronounced change is a tendency towards cholestasis in the last trimester and in a small percentage of women symptoms of jaundice/pruritus develop (intrahepatic cholestasis of pregnancy);  serum bile acids may be useful and very occasionally, it may be necessary to determine whether a raised ALP level is of placental or liver origin.

Request Form

Request on ICE


On request, after discussion with a Clinical Biochemist

Specific Criteria

Investigation of unexplained elevated alkaline phosphatase in childhood. Differentiation of placental alkaline phosphatase from liver in suspected intrahepatic cholestasis of pregnancy. Other requests must be agreed with Consultant Biochemist.

Turnaround Time

1 month


Serum in gold-top vacutainer


2 ml


Vacutainer gold top

Lab Handling

Sent to referral laboratory (Great Ormond Street)


No specific collection conditions

Lab Handling

Aliquot and store at 4C.

Causes for Rejection

Normal alkaline phosphatase level.  Unlabelled or incorrectly labelled sample