How is it used?
In conditions affecting the liver, damaged cells in the liver release increased amounts of ALP into the blood. This test is often used to detect blocked bile ducts because ALP is especially high in the cells that line bile ducts. If one or more of them are obstructed, for example by a tumour, then blood levels of ALP will often be high.
Any condition that affects bone growth or causes increased activity of bone cells can affect ALP levels in the blood. An ALP test may be used, for example, to detect cancers that have spread to the bones or to help diagnose Paget's disease, a condition that causes malformed bones. This test may also sometimes be used to monitor treatment of Paget's disease or other bone conditions, such as vitamin D deficiency.
When is it requested?
ALP is generally part of a routine laboratory test profile called liver function tests. It is usually requested with several other tests if a patient has of a liver or bone disorder.
What does the test result mean?
Raised levels of ALP are usually due to a disorder of either the bone or liver. If other liver function tests such as bilirubin, gamma-glutamyl transferase (GGT), alanine aminotransferase (ALT) or aspartate aminotransferase (AST) are also raised, this usually indicates that the ALP is coming from the liver. However if other liver function tests are normal, this suggests that the ALP might be coming from bone. In some forms of liver disease, such as hepatitis, ALP is usually much less elevated than AST or ALT. However, when the ducts are blocked (for example by gallstones, scars from previous gallstones or surgery, or by a ), ALP and bilirubin may be increased much more than either AST or ALT. ALP can also be raised in bone diseases such as Paget’s disease (where bones become enlarged and deformed), vitamin D deficiency, healing fractures or in certain cancers that spread to bone.
30- 110 U/L
0 days to 1 week 80–380 U/L
1 week - 4 weeks 120–550 U/L
4 weeks - 26 weeks 120–650 U/L
26 weeks - 2 years 120–450 U/L
2 years - 6 years 120–370 U/L
6 years - 10 years 120–440 U/L
10 years - 14 years 130–530 U/L
14 years - 15 years 105–480 U/L
15 years - 17 years 80–380 U/L
17 years - 19 years 50–220 U/L
19 years - 22 years 45–150 U/L
10 years - 13 years 100–460 U/L
13 years - 14 years 70–330 U/L
14 years - 15 years 50–280 U/L
15 years - 16 years 35–140 U/L
16 years - 22 years 30–110 U/L
The reference intervals shown above are known as a harmonised reference interval. This means that eventually all laboratories in Australia will eventually use this same interval so wherever your sample is tested, the reference interval should be the one shown above. Laboratories are in the process of adopting these harmonised intervals so it is possible that the intervals shown on the report of your results for this test may be slightly different until this change is fully adopted. More information can be found under Reference Intervals – An Overview
Is there anything else I should know?
Pregnancy can increase ALP levels. Children have higher ALP levels because their bones are growing and ALP is often very high during the 'growth spurt' which occurs at different ages in males and females. Occasionally young children may have a very high ALP level for a short time and this is not a sign of disease.
Eating a meal, particularly if it contains a lot of fat, can increase the ALP level slightly for a few hours in some people. Ideally the test should be done after fasting overnight. Some drugs may increase ALP levels, including oral contraceptives, some antibiotics and especially some of the drugs used to treat psychiatric problems or epilepsy, but significant increases are rare.