An AST (aspartate aminotransferase) test is a common blood examination that assesses the function of certain organs. This test measures the level of a specific enzyme in the bloodstream. It indicates potential cell damage in various tissues.
Understanding AST’s Function
Aspartate aminotransferase (AST) is an enzyme found in various tissues throughout the body, with high concentrations in the liver, heart, skeletal muscles, and kidneys. This enzyme plays a role in amino acid metabolism. When cells in these organs become damaged or inflamed, AST can leak from the affected tissues into the bloodstream. This leakage increases AST levels in the bloodstream, indicating cellular injury.
Reasons for an AST Test
Healthcare providers may order an AST test for various reasons, often as part of routine blood work or a liver panel. Doctors recommend an AST test if an individual experiences symptoms suggestive of liver issues, such as unexplained fatigue, nausea, vomiting, or abdominal pain. Other symptoms that prompt testing include jaundice (yellowing of the skin or eyes), dark urine, or unexplained muscle weakness. The test is also used to monitor liver health in individuals with existing liver conditions, those taking medications that could affect the liver, or people with risk factors like diabetes or obesity.
Deciphering Your AST Results
AST test results are compared to a normal range, though these ranges can vary slightly between laboratories based on age, sex, and testing methods. Normal AST levels for adults are generally between 8 to 48 units per liter (U/L) for males and 8 to 43 U/L for females.
Elevated AST levels suggest cell damage in the liver or other organs where the enzyme is present. Mild increases may not always signify a serious condition, as strenuous exercise or a fatty meal can temporarily raise levels. Higher elevations indicate more significant cellular injury. Very high AST levels, sometimes exceeding 500 U/L, may indicate acute viral hepatitis or severe liver damage. An AST result alone does not provide a complete diagnosis; healthcare providers consider it alongside other tests, particularly alanine aminotransferase (ALT), and a person’s overall health.
What Affects AST Levels
Many factors can influence AST levels. Liver conditions are a common cause of elevated AST, including various forms of hepatitis, cirrhosis (scarring of the liver), and alcohol-related liver disease. Metabolic dysfunction-associated steatotic liver disease, previously known as nonalcoholic fatty liver disease, can also lead to increased AST.
Damage to other organs rich in AST can also elevate its levels. This includes muscle injuries, such as those from extreme exercise, trauma, or conditions like rhabdomyolysis or muscular dystrophy. Heart attacks or congestive heart failure can also result in higher AST readings. Certain medications are known to affect AST levels, including some antibiotics, anti-seizure drugs, statins, and even over-the-counter pain relievers like acetaminophen, especially in high doses. Other factors include kidney disease, mononucleosis, hemochromatosis, deep burns, and pregnancy complications like preeclampsia.