Liver Function Markers – Lab Values Explained
Liver function markers are blood test values that provide information about the health and function of the liver. They help doctors detect and monitor liver diseases at an early stage.
Things worth knowing about "Liver Function Markers"
Liver function markers are blood test values that provide information about the health and function of the liver. They help doctors detect and monitor liver diseases at an early stage.
What Are Liver Function Markers?
Liver function markers (also known as liver function tests or LFTs) are laboratory parameters measured in the blood to assess the health and function of the liver. They play a central role in diagnosing and monitoring liver diseases, as well as in supervising certain drug therapies that may affect the liver.
The liver is the largest metabolic organ in the human body, responsible for detoxifying the blood, producing proteins and bile, and regulating carbohydrate and fat metabolism. Damage to liver tissue is often reflected in altered blood test values.
Key Liver Function Markers at a Glance
Transaminases (Aminotransferases)
Transaminases are the most well-known liver markers and indicate liver cell damage:
- ALT (Alanine Aminotransferase): Highly liver-specific; elevated in hepatitis, fatty liver disease, and toxic liver injury.
- AST (Aspartate Aminotransferase): Also found in heart and skeletal muscle; significantly elevated in severe liver damage.
Cholestasis Markers
These markers indicate impaired bile flow (cholestasis):
- GGT (Gamma-Glutamyltransferase): A sensitive marker for alcohol consumption, biliary tract diseases, and drug-induced liver injury.
- ALP (Alkaline Phosphatase): Elevated in biliary tract disorders, but also in bone and intestinal diseases.
- Bilirubin: A breakdown product of the red blood cell pigment haemoglobin; elevated levels cause jaundice (icterus).
Synthesis Parameters
These values measure the liver capacity to produce vital substances:
- Albumin: The most important transport protein in the blood; reduced in chronic liver diseases.
- Prothrombin Time (PT) / INR: Measures blood clotting ability; since clotting factors are produced in the liver, this value is altered in liver dysfunction.
- Cholinesterase (CHE): An enzyme produced exclusively in the liver; reduced in chronic or severe liver damage.
Additional Relevant Markers
- LDH (Lactate Dehydrogenase): A non-specific marker of cell damage, also elevated in liver disease.
- AFP (Alpha-Fetoprotein): A tumour marker used when hepatocellular carcinoma (liver cancer) is suspected.
When Are Liver Function Markers Measured?
Liver function markers are used in various clinical situations:
- To investigate symptoms such as fatigue, jaundice, upper abdominal pain, or dark urine
- When a liver disease is suspected (e.g., hepatitis, fatty liver, liver cirrhosis)
- For monitoring the progression of known liver conditions
- To supervise medications that may strain the liver (e.g., statins, certain antibiotics)
- As part of preventive check-ups or routine blood work
Interpreting Liver Function Markers
The interpretation of liver function markers must always be done in clinical context. Individual elevated values are not always pathological, but they can indicate serious conditions. The pattern of changes is particularly important:
- Predominantly elevated transaminases: Hepatocellular pattern – suggests hepatitis, fatty liver, or alcohol or drug-induced liver damage
- Predominantly elevated GGT and ALP with bilirubin: Cholestatic pattern – suggests biliary tract problems or gallstones
- Reduced synthesis parameters (albumin, PT): Suggests advanced liver function impairment
Diagnosis and Further Investigations
When liver function markers are abnormal, further investigations are typically initiated, including:
- Abdominal ultrasound (liver sonography)
- Specific serological tests (e.g., hepatitis serology)
- Imaging procedures such as CT or MRI
- In certain cases: liver biopsy for histological examination
References
- European Association for the Study of the Liver (EASL) – Clinical Practice Guidelines on Non-invasive Tests for Evaluation of Liver Disease Severity and Prognosis. Journal of Hepatology, 2021.
- Friedman, L.S. – Approach to the Patient with Abnormal Liver Biochemical and Function Tests. UpToDate, 2023.
- Limdi, J.K., Hyde, G.M. – Evaluation of abnormal liver function tests. Postgraduate Medical Journal, 2003; 79(932): 307–312.
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