The liver function tests (LFTs) are a group of blood tests used to assess the health and function of your liver. These tests measure various enzymes, proteins, and other substances produced by the liver.
Common Liver Function Tests
Here's a breakdown of the typical tests included in a liver function panel:
Liver Enzymes
These enzymes are released into the bloodstream when liver cells are damaged.
- Alanine Transaminase (ALT): Primarily found in the liver, high levels often indicate liver damage.
- Aspartate Transaminase (AST): Found in the liver, heart, muscles, and other tissues. High levels can signal liver damage or issues in other organs.
- Alkaline Phosphatase (ALP): Found in the liver, bones, and intestines. High levels may indicate liver or bone disorders.
- Gamma-Glutamyl Transferase (GGT): Often used to help differentiate the cause of high ALP levels and can indicate bile duct issues or alcohol abuse.
Liver Proteins
These tests measure the liver's ability to produce proteins.
- Total Protein: Measures the total amount of protein in the blood.
- Albumin: The main protein produced by the liver. Low levels can suggest liver disease or malnutrition.
Bilirubin
This test measures the amount of bilirubin, a yellow pigment made during the breakdown of red blood cells and processed by the liver.
- Serum Bilirubin: Elevated levels indicate a problem with the liver's ability to process bilirubin, leading to jaundice.
Blood Clotting Factors
These tests measure the liver's ability to make proteins needed for blood clotting.
- Prothrombin Time (PT): Measures how long it takes for blood to clot.
- International Normalized Ratio (INR): A standardized way of reporting PT results, used particularly for those on blood thinners and for liver function assessment.
Understanding Results
Elevated or decreased levels in any of these tests can suggest underlying liver issues. A doctor will interpret these results within the context of your overall health and medical history. It's also important to note that some medications can affect your LFT results.
Summary Table of Liver Function Tests
| Test Name | What It Measures | Potential Implications of Abnormal Levels |
|---|---|---|
| Alanine Transaminase (ALT) | Liver-specific enzyme; Indicates liver cell damage | High levels often suggest liver injury, disease, or inflammation. |
| Aspartate Transaminase (AST) | Enzyme present in liver, heart, muscle; Indicates organ damage | Elevated levels might suggest liver disease, heart attack, or muscle injury. |
| Alkaline Phosphatase (ALP) | Enzyme present in the liver, bones, bile ducts | Increased levels might point to liver or bile duct issues or bone problems. |
| Gamma-Glutamyl Transferase (GGT) | Enzyme present in the liver, bile ducts | Elevated levels might indicate bile duct obstruction or alcohol abuse. |
| Total Protein | Total amount of protein in the blood | Abnormal levels may indicate various issues including liver disease, malnutrition, or kidney disease. |
| Albumin | Main protein produced by the liver | Low levels can indicate liver disease, kidney issues, or malnutrition. |
| Serum Bilirubin | Breakdown product of red blood cells processed by the liver | Elevated levels often cause jaundice and can suggest liver or bile duct problems. |
| Prothrombin Time (PT) | Time it takes for blood to clot | Longer clotting times might indicate liver damage or issues with clotting factors. |
| International Normalized Ratio (INR) | Standardized PT result used for people on blood thinners and assessing liver function | Elevated INR levels might suggest a high risk of bleeding, often seen with liver damage. |
