Liver Function Test
A liver function test (LFT) is a group of blood tests used to assess the health and function of the liver. These tests measure the levels of enzymes, proteins, and other substances produced or cleared by the liver. Abnormal results can indicate liver damage, disease, or other conditions affecting liver function.
Components of a Liver Function Test
The LFT panel typically includes the following measurements:
- Liver Enzymes
- Alanine Aminotransferase (ALT): An enzyme found primarily in the liver. Elevated levels indicate liver damage or inflammation.
- Aspartate Aminotransferase (AST): An enzyme found in the liver, heart, and muscles. High levels may suggest liver or muscle damage.
- Alkaline Phosphatase (ALP): An enzyme related to the bile ducts and bones. Elevated levels can indicate bile duct obstruction or bone disorders.
- Gamma-Glutamyl Transferase (GGT): An enzyme that rises with bile duct problems or alcohol-related liver damage.
- Proteins
- Albumin: A protein made by the liver. Low levels may indicate chronic liver disease or malnutrition.
- Total Protein: Measures the total amount of protein in the blood, including albumin and globulins.
- Bilirubin
- Total Bilirubin: A waste product from the breakdown of red blood cells. High levels can indicate liver dysfunction or bile duct obstruction.
- Direct (Conjugated) Bilirubin: Measures bilirubin that has been processed by the liver. Elevated levels suggest a problem with bile flow.
- Indirect (Unconjugated) Bilirubin: Measures bilirubin that has not yet been processed by the liver. High levels may indicate excessive red blood cell breakdown.
- Prothrombin Time (PT)
- Measures how long it takes for blood to clot. The liver produces clotting factors, so prolonged PT may indicate liver damage.
Why Are Liver Function Tests Done?
LFTs are used to:
- Diagnose liver diseases such as hepatitis, cirrhosis, or fatty liver disease.
- Monitor the progression of liver disease or the effectiveness of treatment.
- Assess the impact of medications or toxins on the liver.
- Evaluate overall liver health before surgery or other medical procedures.
- Investigate symptoms like jaundice, abdominal pain, fatigue, or dark urine.
Common Conditions Detected by LFTs
- Hepatitis: Inflammation of the liver caused by viruses, alcohol, or toxins.
- Cirrhosis: Scarring of the liver due to chronic damage.
- Fatty Liver Disease: Buildup of fat in liver cells.
- Bile Duct Obstruction: Blockage in the bile ducts, often due to gallstones or tumors.
- Liver Cancer: Abnormal growths in the liver.
- Medication-Induced Liver Injury: Damage caused by drugs or supplements.
Interpreting Results
- Elevated ALT and AST: Suggest liver cell damage (e.g., hepatitis).
- Elevated ALP and GGT: May indicate bile duct obstruction or cholestasis.
- Low Albumin: Can indicate chronic liver disease or malnutrition.
- High Bilirubin: May suggest liver dysfunction or hemolysis (breakdown of red blood cells).
- Prolonged PT: Indicates impaired liver function affecting blood clotting.
Limitations of LFTs
- LFTs alone cannot diagnose a specific condition; they provide clues that require further investigation.
- Some liver diseases may not show abnormalities in LFTs until significant damage has occurred.
If you have abnormal LFT results, your healthcare provider may recommend additional tests, such as imaging (ultrasound, CT, or MRI) or a liver biopsy, to determine the underlying cause. Always consult a doctor for proper interpretation and guidance.
