AST, or Aspartate Amino Transferase test, is an enzyme-based blood test employed for determining the amount of aspartate transferase in a given sample of blood. Although it can be measured alone, the AST Blood Test is often part of a broader panel of tests, including a liver panel or comprehensive metabolic panel. Let's understand the related aspects of this blood test in detail.

What is the AST Blood Test?

Alternatively called the SGOT (Serum Glutamic-Oxaloacetic Transaminase) test, the AST (Aspartate Amino transferase) test helps assess liver function and monitor chronic liver diseases. 

Aspartate transferase is an enzyme found in the liver and the heart. This enzyme assists most of the important bodily processes. Being present in the liver, the AST enzyme can be found in various tissues in the body. This enzyme is released into the bloodstream in the event of cell damage, thereby raising the level of AST in the blood. Thus, when the AST Blood Test is high, it may be an indication of a health condition that should be further looked into through additional testing. AST blood test values may throw light upon conditions or diseases concerning the liver and heart.

Purpose of AST Blood Test

An AST Blood Test is often employed for the purpose of detection of cell damage. In a majority of cases, it is used for the assessment of liver function. However, it can provide insight into various other health conditions as well.

Depending on the reason for a doctor's recommendation of an AST Blood Test, it can be employed for the purpose of diagnosis, screening, or monitoring various health conditions. 

• Screening: This test may be prescribed for assessing an individual against certain risk factors such as obesity, diabetes, having a family history of liver problems, alcohol abuse, etc. It can be prescribed during routine check-ups and as part of a comprehensive metabolic panel.
• Diagnosing: An AST test is also used as a part of diagnostic testing based on the symptoms experienced by an individual. In the case of liver diseases and conditions, the AST test may provide an idea of the condition based on symptoms like jaundice, swelling, inflammation, unexplained weight loss, nausea and vomiting, etc.
• Monitoring: This process involves using an AST test to keep a tab on how a situation pans out for an individual under observation or treatment for a certain health condition. Sometimes, the tests may be repeated to track and check liver health or the progress of treatment. An AST test as part of a liver test panel may help show signs of liver damage if a person has to start on a medication that may potentially be harmful to the liver.

When is an AST Blood Test needed?

An AST Blood Test may be beneficial for patients with a diverse range of medical conditions. A liver test panel and a comprehensive metabolic panel incorporate the AST test as an emergency or general diagnostic test to confirm or rule out conditions associated with symptoms that may cause various health problems. In the case of liver disease, a liver test panel may be beneficial for doctors to learn about the cause and severity of the condition in a patient.

Furthermore, patients who have known risk factors or are at high risk of developing diseases or conditions that may potentially harm the liver may benefit from regular AST screening tests to monitor any cell damage. Sometimes, it may be recommended for those who may not have any risk factors for liver diseases. In some cases, doctors may recommend an AST test for monitoring a certain health condition or when a person starts on a new medication.

Uses of AST Blood Test 

An AST test is used for investigating the reason for various liver diseases and estimating the severity and prognosis of liver disease or failure. The AST test procedure identifies an elevation in the AST enzyme levels, which is reflected in the AST test report. 

The AST test can be used for detecting liver-related diseases such as:

• Infection or viral hepatitis
• Fatty liver 
• Abscess in liver
• Liver trauma
• Liver cirrhosis 
• The circulatory collapse of the liver
• End-stage liver disease
• Liver cancer

Other diseases that can be diagnosed and monitored with the help of the AST test include inflammation of the pancreas, known as pancreatitis, and various heart problems.

How do you prepare for the AST Blood Test?

Before the AST Blood Test is performed, the doctor may recommend fasting for a period of time as the test involves the activity of enzymes and other compounds. This insinuates that the patient shouldn't consume food or drinks for a certain period of time (typically up to 12 hours) before the test is performed. Additional instructions may be provided by the concerned doctor based on the reason for which the test is performed.

In some cases, certain supplements or medications may also influence these enzymes, and intake of such products may be restricted for a certain amount of time by the doctor. In case only the AST is measured, the patient may not need to fast. However, patients should follow the specific instructions provided by their concerned doctor.

What happens during the AST Blood Test?

During the AST Blood Test, a sample of blood taken from a patient is tested in a laboratory to assess the amount of AST enzyme present in the blood sample. This can be compared against reference levels and interpreted accordingly to get the status of a certain health condition.

AST Blood Test Procedure

The AST test involves drawing a sample of blood from a vein in the arm. It may be performed at home or at a doctor's office by a phlebotomist. The patient may be advised to remain seated in a relaxed position while a stretchy band is put around the upper arm so that there is a greater flow of blood in the lower part of the arm. The area of the arm from where the blood has to be drawn may be cleaned with an antiseptic liquid wipe. Subsequently, the phlebotomist used a syringe to draw blood into a vial to be tested further in the laboratory.

What do AST Blood Test results mean (if they are low and higher than normal levels)?

After the AST test reports come back, the doctor may help interpret it for the patients and understand the AST Blood Test values. The AST Blood Test levels may be different for different patients based on their age and gender. The AST levels normal values may differ from one laboratory to another, which may provide different reference ranges. The test reports may be interpreted accordingly.

The AST Blood Test is measured in units per litre. For reference, here are the normal ranges for AST tests in blood for different ages and genders. 

• Males: 17–59 U/L
• Females: 14–36 U/L
• Elderly: Slightly higher values in the respective genders

The AST Blood Test values may be higher than normal. Different degrees of elevation in AST levels may mean different things.

• Slightly elevated than normal: A slow but persistent rise in AST levels may cause more significant damage than a one-time rise in AST levels. It may be caused due to chronic alcoholism, but a specific diagnosis may be required.
• Moderately high: When it is found that AST Blood Test is high, it may mean and help doctors to diagnose the following conditions:
• Cholestasis - a condition of reduced bile flow from the liver
• Muscle trauma
• Muscular dystrophy or progressive loss of muscles 
• Risk of heart attacks and heart failure
• Pulmonary embolism
• Very high: When doctors find the level of AST Blood Test high, it may mean that the amount of AST found in blood is almost ten times higher than typical values. This may help doctors identify conditions like:
  • Acute viral hepatitis or severe inflammation of the liver 
  • Liver cirrhosis, which is irreversible scarring or fibrosis of the liver
  • Liver intoxication
  • End-stage liver failure
  • Tumour necrosis 

There are many things to be considered while interpreting AST test values. Additional tests may be recommended to cross-verify or confirm a suspected condition. The ALT enzyme may be measured alongside the AST enzyme for a more specific diagnosis and to get a clearer picture of the targeted condition to be diagnosed.

Conclusion

The AST test is an important blood test that is recommended by medical professionals for certain liver problems. The AST test results may be interpreted alone but are considered as part of a panel of tests more often, thereby facilitating the diagnosis of a particular suspected condition.

FAQs 

Q1. What is a normal level of AST Blood Test?

The normal AST Blood Test level may vary from person to person based on age and gender but may range between 14 and 60 units/litre of blood.

Q2. What happens if the AST blood test is positive?

A higher-than-normal level of AST in blood samples may indicate an underlying health condition or disease that necessitates further investigation.

Q3. What happens if the AST Blood Test is negative?

When an AST test is negative, it is generally considered to be normal. However, additional tests may still be required to confirm or rule out other possible reasons for symptoms experienced by a person.

Q4. What is the difference between ALT and AST in blood tests?

ALT or Alanine Amino Transferase is another enzyme present in the liver alongside AST, which has a higher concentration than AST and is often considered to be measured to check liver function and diagnose various conditions and diseases of the liver.

Q5. What level of AST is alarming?

AST levels more than ten times the typical values may be signs of liver injury or hepatitis.