Alkaline phosphatase is an enzyme that is involved in a wide range of processes and is found in many parts of the body, particularly the liver, intestines and bones. It is often high in people with liver or bone disease. The ALP test is often requested with other tests if someone has symptoms of a liver or bone disorder. It is included as part of a panel of tests performed on the same blood sample called Liver Function Tests (LFTs). It is also used to help diagnose bone disease such as Paget’s disease and cancer. ALP can also be elevated in some gastrointestinal diseases.
Why get tested?
ALP levels are affected by a wide range of health conditions. Abnormally high levels of ALP in your blood can suggest a problem with your liver or bones. If the liver is damaged, liver cells release increased amounts of ALP. The test is often used to detect blocked bile ducts because ALP is especially high in the cells that line the bile ducts of the liver. If one or more of them are obstructed, for example, by gallstones or a tumour, then blood levels of ALP will often be high.
Having the test
Reading your test report
Your results will be presented along with those of your other tests on the same form. You will see separate columns or lines for each of these tests.
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 bile ducts of the liver are blocked (for example by gallstones, scars from previous gallstones or surgery, or by a tumour), ALP may be increased much more than either AST or ALT and the bilirubin may also be raised.
Sometimes it is not clear if ALP is raised due to liver disease or bone disease. Your doctor may order a test such as ALP isoenzymes to help work this out.
If test results suggest that the raised ALP levels are due to bone disease, your doctor will need to investigate further.
Children have higher levels of ALP than adults because their bones are growing. A person recovering from a bone injury may also have a raised ALP level while their bone heals.
It is also common to have higher ALP levels than usual during the second and third trimesters of pregnancy.
Your results will be compared to reference intervals (sometimes called a normal range).
If your results are flagged as high or low this does not necessarily mean that anything is wrong. It depends on your personal situation. Your results need to be interpreted by your doctor.
ALP Reference Intervals
The reference intervals for this test are common reference intervals which means that all laboratories in Australia should be using this same target range.
Many factors affect ALP levels apart from disease including age, blood type, and gender. Hence there are age and gender specific common ranges as indicated below.
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 45-170 U/L
16 years - <22 years 35-140 U/L
Questions to ask your doctor
The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.
You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.
Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:
Anymore to know
Other commonly used liver function tests include other enzymes found in liver cells, such as alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), aspartate aminotransferase (AST), and bilirubin (a breakdown product of red blood cells).
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