Liver Function Tests (LFTs)


What are the Liver Function Tests (LFTs)?

Liver Function Tests (LFTs) play a crucial role in assessing the health and functionality of one of the body’s most vital organs—the liver. These tests provide valuable insights into various aspects of liver health, helping gastroenterologists diagnose and monitor a wide range of liver-related conditions. Let’s look at the significance of LFTs, the individual components of these tests, common abnormalities, and the clinical implications of abnormal results.

The Significance of Liver Function Tests:

The liver is a multifunctional organ responsible for essential processes such as metabolism, detoxification, and the production of proteins necessary for blood clotting and immune function. LFTs are a panel of blood tests designed to evaluate how well the liver is performing these functions. Common LFTs include alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), gamma-glutamyl transferase (GGT), total bilirubin, direct bilirubin, and serum albumin.

Individual Components of Liver Function Tests:

  1. Alanine Aminotransferase (ALT):
    • ALT is an enzyme found primarily in the liver.
    • Elevated ALT levels may indicate liver injury or inflammation, commonly associated with conditions such as hepatitis and fatty liver disease.
  2. Aspartate Aminotransferase (AST):
    • AST is an enzyme present in various tissues, including the liver and heart.
    • Elevated AST levels can be indicative of liver damage but are less specific than ALT.
  3. Alkaline Phosphatase (ALP):
    • ALP is an enzyme found in the liver, bones, and other tissues.
    • Increased ALP levels may suggest liver or bone disorders, such as obstruction of bile ducts or bone diseases.
  4. Gamma-Glutamyl Transferase (GGT):
    • GGT is an enzyme found in the liver, bile ducts, and kidney.
    • Elevated GGT levels may signal liver or bile duct issues, and it is often used to assess alcohol consumption.
  5. Bilirubin:
    • Bilirubin is a yellow pigment produced during the breakdown of red blood cells.
    • Increased bilirubin levels can result from liver dysfunction and may manifest as jaundice.
  6. Serum Albumin:
    • Albumin is a protein produced by the liver that helps maintain blood volume and pressure.
    • Low albumin levels may indicate chronic liver disease or malnutrition.

Abnormalities in Liver Function Tests:

  1. Elevated Alanine Aminotransferase (ALT):
    • Significance: ALT is primarily found in the liver, and elevated levels suggest liver cell damage or inflammation.
    • Possible Causes:
  2. Elevated Aspartate Aminotransferase (AST):
    • Significance: Like ALT, AST is an enzyme found in the liver, but it is also present in other tissues.
    • Possible Causes:
      • Similar to ALT, but AST is less specific to the liver.
      • Alcohol-induced liver injury
      • Cirrhosis
      • Heart conditions (since AST is also found in heart muscle)
  3. Alkaline Phosphatase (ALP) Elevation:
    • Significance: ALP is present in the liver, bones, and bile ducts. Elevated levels suggest obstruction or damage.
    • Possible Causes:
      • Biliary obstruction (e.g., gallstones, tumors)
      • Liver diseases (cirrhosis, hepatitis)
      • Bone disorders (Paget’s disease, fractures)
  4. Gamma-Glutamyl Transferase (GGT) Elevation:
    • Significance: GGT is elevated in conditions affecting the liver and bile ducts.
    • Possible Causes:
      • Alcohol abuse
      • Liver diseases (hepatitis, cirrhosis)
      • Biliary diseases (bile duct obstruction)
  5. Bilirubin Abnormalities:
    • Significance: Bilirubin is a product of hemoglobin breakdown. Elevated levels may cause jaundice.
    • Possible Causes:
      • Liver diseases (hepatitis, cirrhosis)
      • Hemolytic anemia
      • Bile duct obstruction
  6. Low Serum Albumin:
    • Significance: Albumin is a protein produced by the liver. Low levels may indicate impaired liver synthetic function.
    • Possible Causes:
      • Chronic liver disease (cirrhosis)
      • Malnutrition
      • Nephrotic syndrome (kidney disorder)
  7. Prothrombin Time (PT) Prolongation:
    • Significance: PT measures blood clotting time. Prolongation suggests impaired liver synthetic function.
    • Possible Causes:
      • Severe liver disease (cirrhosis)
      • Vitamin K deficiency
      • Warfarin use
  8. Aminotransferase Ratio (AST/ALT):
    • Significance: An increased AST/ALT ratio may suggest alcoholic liver disease.
    • Possible Causes:
      • Chronic alcohol consumption
      • Alcoholic hepatitis

Approach to Abnormal LFTs in Primary Care:

The diagnostic approach to abnormal LFTs in primary care is depicted in the following algorithm (Figure).

Clinical Implications of Abnormal LFT Results:

Clinical implications of abnormal Liver Function Test (LFT) results are crucial for gastroenterologists in diagnosing, managing, and monitoring various liver disorders. Abnormalities in LFTs can provide valuable insights into the health of the liver, helping clinicians make informed decisions about patient care. Let’s elaborate on the clinical implications of abnormal LFT results:

  1. Diagnosis of Liver Diseases:
    • Hepatitis: Elevated levels of ALT and AST are indicative of liver inflammation, often associated with hepatitis (viral, alcoholic, autoimmune).
    • Fatty Liver Disease: Increased ALT and AST levels are common in non-alcoholic fatty liver disease (NAFLD), a condition linked to obesity and metabolic syndrome.
    • Cirrhosis: Abnormal LFTs, low albumin, and prolonged PT can suggest advanced liver damage and cirrhosis.
  2. Monitoring Disease Progression:
    • Serial monitoring of LFTs is essential for assessing the progression of liver diseases over time.
    • Trends in ALT, AST, and other markers help gastroenterologists gauge the effectiveness of treatment interventions.
  3. Identification of Specific Liver Disorders:
    • Different patterns of LFT abnormalities can help identify specific liver disorders.
    • For example, an elevated GGT may suggest alcohol-related liver damage, while a high ALP might indicate biliary obstruction.
  4. Assessment of Liver Function:
    • LFTs provide information about the synthetic function of the liver, such as the production of proteins like albumin and clotting factors.
    • Low albumin levels can indicate chronic liver disease, while prolonged PT suggests impaired clotting function.
  5. Risk Stratification:
    • Abnormal LFT results contribute to risk stratification, helping healthcare professionals assess the severity of liver diseases.
    • This information guides decisions regarding the level of medical intervention and the need for specialized care.
  6. Screening for Complications:
    • Abnormal LFTs may prompt further investigation for potential complications of liver diseases.
    • For example, jaundice associated with elevated bilirubin levels may lead to the identification of bile duct obstruction or severe liver dysfunction.
  7. Guiding Treatment Plans:
    • LFT results play a pivotal role in formulating treatment plans for liver disorders.
    • Identifying the underlying cause of abnormal LFTs guides the choice of medications, lifestyle modifications, and interventions to address the specific condition.
  8. Patient Counseling and Education:
    • Abnormal LFT results offer an opportunity for gastroenterologists to counsel patients about the importance of lifestyle changes, medication adherence, and regular follow-up.
    • Education about the implications of abnormal LFTs helps empower patients in managing their liver health.

Bottom line

Liver Function Tests are invaluable tools in assessing the health of the liver and diagnosing various liver disorders. Understanding the individual components of LFTs, their significance, and the potential implications of abnormal results is essential for both gastroenterologists and individuals seeking to maintain liver health. Regular monitoring through LFTs can contribute to the early detection and management of liver conditions, promoting overall well-being.

Also read:

Transaminitis or elevated transaminases ALT & AST

How can I contact gastroenterologist Dr. Zavos for an appointment?

Dr. Chris Zavos is a board-certified gastroenterologist and hepatologist, located in Thessaloniki Greece, and specifically in Kalamaria suburb, about 7 kilometres (4 miles) southeast of downtown Thessaloniki. His private office is at: Fanariou 8 street (near Aigaiou and Adrianoupoleos avenues), Kalamaria (Thessaloniki), Greece.

Thessaloniki International Airport is only 10 km away from his private office in Kalamaria and can be reached by taxi within 13 minutes from the airport.

Dr. Chris Zavos performs endoscopies at Bioclinic private hospital in downtown Thessaloniki (Mitropoleos 86 street).

You can contact Dr. Zavos at phone numbers: (+30)-6976596988 and (+30)-2311283833, or you can email him at Dr. Zavos responds to Greek and English languages.

Last update: 1 May 2024, 17:11


Gastroenterologist - Hepatologist, Thessaloniki

PhD at Medical School, Aristotle University of Thessaloniki, Greece

PGDip at Universitair Medisch Centrum Utrecht, The Netherlands

Ex President, Hellenic H. pylori & Microbiota Study Group