AST

The AST test by Access Medical Labs is a single-biomarker lab test often used in conjunction with other biomarkers to evaluate liver health and function. It can help diagnose and monitor liver diseases, assess the severity of liver damage, and monitor the effectiveness of treatment.  It is commonly ordered as part of a Comprehensive Metabolic Panel to assess kidney and liver function, electrolytes, fluid and acid/base balance in the body.

AST stands for Aspartate Aminotransferase. It is an enzyme found primarily in the liver, heart, skeletal muscles and kidneys. The AST test measures the levels of this enzyme in the blood.

Elevated AST levels can indicate liver damage or disease including hepatitis, cirrhosis, and fatty liver disease.  Non-alcoholic fatty liver disease, or NAFLD, often occurs with type 2 diabetes and insulin resistance and is increasingly common. Elevated AST levels can also be a sign of muscle damage or injury, as AST is released into the bloodstream when muscle cells are damaged.

AST levels can also be elevated due to factors unrelated to liver or muscle damage, such as gallbladder disease, certain medications, strenuous exercise, or recent surgery.

What is AST?

AST, also known as aspartate aminotransferase, is an enzyme found primarily in the liver, heart, skeletal muscle, and kidneys. It plays a crucial role in the metabolism of amino acids and in energy production. Specifically, AST catalyzes the transfer of an amino group from aspartate to alpha-ketoglutarate, resulting in the formation of oxaloacetate and glutamate.

AST is commonly measured in blood tests to assess liver function and detect liver damage or injury. When liver cells are damaged or destroyed, AST is released into the bloodstream, causing increased blood levels. Therefore, elevated AST levels in the blood can indicate liver diseases such as fatty liver disease, hepatitis, cirrhosis, or liver cancer.

AST is often assessed in conjunction with another enzyme, ALT (alanine aminotransferase).  Elevations in both AST and ALT are common in liver damage. 

AST is not specific to the liver and can also be elevated in conditions affecting other organs, such as gallbladder disease, heart attacks, muscle diseases, or kidney damage. Therefore, AST levels should be interpreted in conjunction with other clinical findings and additional tests to determine the underlying cause of the abnormal results.

Who should get an AST test?

AST, or aspartate aminotransferase, is an enzyme found in various tissues of the body, including the liver, heart, muscles, and kidneys. Elevated levels of AST in the blood can indicate liver damage or injury, but it is important to note that AST is not a specific marker for liver disease.  To screen for liver damage, AST is most often considered in conjunction with other markers including ALT, ALP (alkaline phosphatase), GGT (gamma-glutamyl transferase), bilirubin, and occasionally other tests.

Ideal candidates for AST testing include:

Patients with suspected liver disease: AST levels can be used to assess liver function and detect liver damage caused by conditions such as hepatitis, cirrhosis, or fatty liver disease.

Patients with suspected gallbladder disease: AST levels can rise in gallbladder and biliary tract disease in the absence of liver injury.

Patients with symptoms of liver dysfunction: These may include yellowing of the skin and eyes (jaundice), abdominal pain, nausea, vomiting, fatigue, dark urine, or pale stools.

Individuals with a history of alcohol abuse: Chronic alcohol consumption can lead to liver damage, and AST levels can help monitor the extent of liver injury.

Patients taking medications known to cause liver toxicity: Certain medications, such as acetaminophen, statins, or antifungal drugs, can potentially harm the liver. Regular AST testing may be recommended to monitor liver function in such cases.

Individuals with risk factors for liver disease: This includes individuals with a history of viral hepatitis, autoimmune diseases affecting the liver, obesity, diabetes, or a family history of liver disease.

Patients with muscle disorders: AST is also present in muscle tissue, so elevated levels may indicate muscle damage or injury. Patients with symptoms such as muscle weakness, pain, or cramps may be candidates for AST testing.

It is important to note that AST levels alone are not sufficient for diagnosing specific conditions. They should be interpreted in conjunction with other liver function tests, medical history, physical examination, and additional diagnostic tests as necessary. Consulting with a healthcare provider or a functional medicine practitioner is recommended to determine the appropriate testing and interpretation of results.

What is a normal AST range?

The normal range for AST levels can vary slightly depending on the laboratory and the specific testing method used. However, in general, the normal range for AST is:

- For adults: 10 to 40 units per liter (U/L)

- For children: 10 to 50 U/L

These ranges are approximate and can vary slightly between different laboratories. Additionally, certain factors such as age, sex, and underlying medical conditions can influence AST levels. Therefore, it is always recommended to consult with a healthcare professional to interpret the results accurately and in the context of an individual's overall health.

What does high AST indicate?

AST levels increase in the blood in the setting of tissue damage, when cellular enzymes enter the bloodstream. ElevatedAST levels in the blood indicate potential damage or injury to the organs where it is predominantly found. A high AST level can be indicative of several conditions or factors:

Liver diseases: The most common cause of elevated AST levels is liver damage or disease. Conditions such as hepatitis (viral, alcoholic, or autoimmune), cirrhosis, fatty liver disease, or liver cancer can lead to increased AST levels.

Heart conditions: AST is also present in cardiac muscle cells. Elevated AST levels may suggest heart muscle damage, such as a heart attack or myocarditis (inflammation of the heart muscle).

Muscle injury: AST is released into the bloodstream when there is damage to skeletal muscles. Intense exercise, trauma, or conditions like rhabdomyolysis (severe muscle breakdown) can cause elevated AST levels.

Kidney problems: Although AST is not primarily found in the kidneys, high levels can be observed in cases of severe kidney damage or renal failure.

Medications and toxins: Certain medications, such as statins (cholesterol-lowering drugs), can cause liver damage and subsequently elevate AST levels. Additionally, exposure to toxins like alcohol or certain chemicals can also lead to increased AST levels.

Up to 10% of the population may have mildly elevated liver enzymes, which warrants further assessment for common causes of liver damage including metabolic syndrome and insulin resistance. 

It is important to note that a single high AST level does not provide a definitive diagnosis. Further evaluation, including additional lab tests and medical history assessment, is necessary to determine the underlying cause of the elevated AST and guide appropriate treatment. Consulting with a healthcare professional, such as a functional medicine practitioner or a hepatologist, is recommended for proper evaluation and management.

What does low AST indicate?

A low AST level in a lab test typically indicates a lower-than-normal amount of this enzyme in the blood. There can be several reasons for a low AST level, including:

Liver dysfunction: AST is primarily produced in the liver, so a low AST level may indicate impaired liver function. Conditions such as liver cirrhosis, hepatitis, or liver failure can lead to decreased AST production.

Malnutrition: Inadequate protein intake or malnutrition can lead to low AST levels. Since AST is involved in amino acid metabolism, a deficiency in protein can result in reduced AST production. Low AST levels may also mean a vitamin B6 deficiency, as vitamin B6 is a required cofactor for AST.

Genetic disorders: Certain genetic disorders can cause decreased AST levels. For example, a rare condition called pyridoxine-dependent epilepsy is associated with low AST levels due to a deficiency in vitamin B6, which is required for AST synthesis.

Medications: Some medications, such as statins used to lower cholesterol levels, can cause a decrease in AST levels. It is important to consider medication history when interpreting AST results.

Pregnancy: During pregnancy, AST levels may be lower than normal. This is considered a normal physiological change and is not usually a cause for concern.

It is important to note that a low AST level alone may not provide a definitive diagnosis. It is often necessary to consider other lab test results, medical history, and clinical symptoms to determine the underlying cause of the low AST level. Consulting with a healthcare provider or a functional medicine expert is recommended for proper evaluation and interpretation of lab results.

How AST Is Tested?

The AST test is typically done by drawing a blood sample from a vein in the arm; fasting is not required.  In most cases a mobile phlebotomist can come to you, draw your blood, and ship your sample to Access Medical Labs for processing the same day.  Access Medical Labs is a CLIA Certified, CAP Accredited Lab.  Results are usually available within a few days. 

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