What is an Alkaline Phosphatase (ALP) Blood Test? (2023)

An alkaline phosphatase (ALP) blood test evaluates a group of enzymes found in many parts of the body. Elevations in ALP may indicate a problem with the liver,Gall bladder, bile ducts, bones or other organ systems.

Purpose of the trial

The ALP test technically measures the activity of a group of related enzymes (alkaline phosphatases). ALP can be used as a kind of medical marker of certain potential medical problems.

What is Alkaline Phosphatase?

These enzymes speed up certain chemical reactions in the body. The most common version of the ALP test evaluates multiple versions of these enzymes with a single value.

Scientists do not fully understand the physiological role of these enzymes, although they do know that ALP plays a role in bone mineralization.In medicine, alkaline phosphatases are important because their presence in the blood can provide information about damage to specific parts of the body.

Alkaline phosphatase is active in many different tissue types. The most important of these are the bones, liver, gallbladder and bile ducts. However, ALP can also come from other sources, such as the intestines, kidneys, or placenta during pregnancy.

So it's no surprise that measuring ALP can sometimes give clues to problems in these body systems. Abnormalities in ALP can be used along with symptoms, additional tests, and other clinical factors to help diagnose many different medical conditions.

Medical significance

A number of different medical conditions in the liver and throughout the bile duct system can lead to elevated ALP. High ALP levels may indicate a problem with bile duct obstruction. These ducts normally transport bile produced by the liver and stored in the gallbladder to the intestines.

ALP is also elevated in certain diseases that affect the bones or the amount of calcium in the blood. Examples include;Paget's disease, hyperparathyreoïdie ofvitamin D deficiency.

Less commonly, other groups of medical conditions can reduce ALP, including malnutrition, hypothyroidism, and pernicious anemia.

Often, but not always, ALP is tested at the same time as several blood tests commonly used to diagnose liver disease, such asaspartate aminotransferase (AST) en (alanine aminotransferase (ALT). These tests may be done if you have liver disease or if you have symptoms suggestive of liver or gallbladder disease.

This may be necessary, for example, if you have jaundice, abdominal pain and nausea. Your doctor may also ask you to take ALP if you have symptoms that could be due to a bone disorder, such as bone pain.

Risks and contraindications

ALP is a simple blood test. Therefore, there are few contraindications. You may experience pain and bruising at the site of the blood draw. Contamination is also a minimal risk.

If you have a bleeding disorder or are taking a medicine that inhibits blood clotting, such as Coumadin, you may have an increased risk of bleeding. Before the test, make sure your doctor knows about all your medical conditions and medications.

For the trial

An overnight fast is usually recommended before taking an ALP test because fatty meals can affect the results by temporarily raising ALP levels.You may want to wear a loose shirt so that the phlebotomist can easily assess a vein in your upper arm.

The test can be performed in a hospital or an outpatient clinic. Usually the process only takes a few minutes.

During the test

To perform the test, a healthcare provider must take a blood sample. First they clean the area. A tourniquet is then applied over the vein to be used, usually in the upper arm.

You may be asked to clench your fist while your phlebotomy finds a good vein to use. The needle is inserted into a vein in your arm. This usually only hurts for a moment or two.

The sample is drawn into a labeled tube to be sent to the laboratory. The needle is removed and the blood collection site is covered with a bandage or tape.

After the trial

The sample is immediately sent to a medical laboratory for analysis. You can usually resume your normal activities right away.

If you feel dizzy after the blood draw, you may need to sit down or have something to eat or drink before continuing with the rest of your day. You may have pain or bruising where your blood was drawn.

Interpretation of results

The test results should come back fairly quickly, within a day or so. Different laboratories may have different reference ranges. Roughly speaking, however, levels between 44 and 147 international units per liter (IU/L) are considered normal.

However, interpretation is sometimes a challenge. Normal ALP levels vary with factors such as age, gender, and even blood type. Adolescents may have elevated levels compared to adults due to active bone growth. ALP may also be slightly elevated in smokers compared to non-smokers.

Pregnancy can temporarily raise ALP levels, even if there is no medical problem. ALP can also be temporarily increased by bone fractures or by certain medications.

These factors should be considered when making a diagnosis. Your healthcare provider can help you interpret your lab results and tell you if there is anything to worry about.

High ALP levels

Clinicians consider the degree of elevation when evaluating ALP levels in a medical context. For example, ALP is often four times higher than normal, or even higher in medical conditions that block the flow of bile out of the body. For example, this could be due to cancer blocking the ducts, gallstones in the bile ducts, or other causes.

Very high levels can also be found if significant liver damage causes bile to flow poorly from the ducts. This can happen due to an autoimmune diseaseprimary biliary cholangitisliver damage from drug use or severe hepatitis from alcohol use. Diseases that invade the liver can also cause this problem, such as cancer,sarcoidosisof amyloidosis.

If the height isn't that high, then other possibilities are more likely. This can be done, for example, by:

• Cirrhosis of the liver
• Viral hepatitis
• Congestive heart failure
• Abdominal infections
• Hodgkin lymphoma
• Hyperparathyreoïdie
• Hyperthyroidism
• Osteomyelitis
• Bone cancer, or cancer that has spread to the bones
• Osteomalacia

Low ALP levels

While high ALP levels are more common than low levels, low levels can be medically significant in some cases. For example, low ALP levels are sometimes found in the following medical conditions:

• Hypothyroidism
• Wilson's disease
• Zinc deficiency
• Pernicious anemia
• celiac disease
• Congenital hypophosphatasia

ALP can be used in the diagnosis of these and related conditions. It is also sometimes used to monitor these conditions after treatment.

I follow

You may not need a comprehensive medical evaluation if your ALP is only slightly elevated. Instead, your doctor may choose to monitor you with repeat blood tests. A slightly elevated ALP can occur in some people, even though there is no real problem. However, high levels require further medical investigation.

Follow-up testing depends on the medical context: your symptoms and physical exam, other past and present medical conditions, other test results, etc. You may have taken the ALP test as part of itother tests to help evaluate the liver, which can provide more information about what your test results mean. If not, other blood tests that are often given to evaluate the liver may be needed.

Sometimes it is helpful to have a specific blood test called γ-glutamylpeptidase (GGTP) if someone's ALP is elevated. This test can help determine if the liver is the source of the growth or if it comes from somewhere else.

Sometimes it is also helpful to perform another type of ALP test (electrophoresis). This test provides information on the fraction of ALP coming from different organs, indicating the likely organ of concern.Usually these tests find the increase due to bone disease or problems with the liver or gallbladder.

Other blood tests may also be needed, depending on the context. For example, if your doctor is concerned that hepatitis may be the cause of your symptoms and ALP results, you may need to be tested for the hepatitis B and hepatitis C virus. Additional blood tests, such as anti-mitochondrial antibody (AMA), may also be needed. . AMA is a blood test that helps diagnose primary biliary cholangitis, a disease that damages the bile ducts in the liver and mainly affects women.

Abdominal ultrasoundit may also be useful as the first imaging modality to evaluate the liver, gallbladder and related structures.If necessary, other techniques can be performed, such as endoscopic retrograde cholangiopancreatography (ERCP) or magnetic resonance cholangiopancreatography (MRCP).

Other tests, such as a liver biopsy, may be necessary in certain circumstances. Your doctor will work with you to identify the underlying cause.

A word from Verywell

ALP can be a useful diagnostic test, especially when performed in conjunction with other related tests. But your ALP may be slightly elevated, even if there's no real cause for concern. Talk to your doctor about all your questions. Together you can draw up the best possible diagnostic and treatment plan.