From the Guidelines
Liver function tests (LFTs) should be analyzed by evaluating patterns of abnormalities rather than focusing on individual values, as recommended by the most recent guidelines 1. When analyzing LFTs, it is essential to consider the clinical context, including patient symptoms, risk factors, and medication history. The initial investigation should include bilirubin, albumin, ALT, ALP, and GGT, together with a full blood count if not already performed within the previous 12 months 1.
Key Considerations
- Start by checking for hepatocellular injury (elevated ALT/AST), cholestatic patterns (elevated alkaline phosphatase, GGT, bilirubin), or mixed patterns.
- For mild elevations (less than 2-3 times normal), monitor and investigate potential causes like medications, alcohol use, obesity, or viral hepatitis.
- For moderate elevations (3-10 times normal), consider more urgent evaluation including hepatitis serologies, autoimmune markers, and imaging studies.
- For severe elevations (greater than 10 times normal), immediate medical attention is required to rule out acute liver failure.
Interpreting Results
- Consider the AST/ALT ratio (>2 suggests alcoholic liver disease) 1.
- Evaluate the degree of bilirubin elevation (direct vs. indirect).
- Assess the presence of synthetic dysfunction (low albumin, prolonged PT/INR).
- Remember that some conditions like fatty liver disease may show minimal LFT abnormalities despite significant disease.
Serial Testing
- Serial testing is often more valuable than isolated results, as trends can reveal disease progression or improvement.
- The clinical context, including patient symptoms, risk factors, and medication history, is essential for proper interpretation of liver function tests 1.
From the Research
Liver Function Tests (LFTs) Analysis
The analysis of liver function tests (LFTs) is a crucial aspect of diagnosing and managing liver disease. LFTs include a range of biochemical parameters, such as:
- AST (aspartate aminotransferase)
- ALT (alanine aminotransferase)
- GGT (gamma-glutamyl transferase)
- Alkaline phosphatase
- Bilirubin levels
- Albumin levels
- Coagulation tests, such as prothrombin activity 2
Interpretation of LFT Results
The interpretation of LFT results is vital in diagnosing liver disease. For example:
- Cytolytic elevation in serum aminotransferases may indicate pharmacological toxicity, viral hepatitis, alcoholic and non-alcoholic fatty liver disease, and hemochromatosis 2
- Cholestatic elevation of serum enzymes may indicate biliary obstruction or intrahepatic cholestasis, such as primary biliary cirrhosis (PBC) or primary sclerosing cholangitis (PSC) 2
- Hyperbilirubinemia may indicate hemolysis, ineffective erythropoiesis, or liver dysfunction 2
Role of LFTs in Diagnosing Liver Disease
LFTs play a crucial role in diagnosing liver disease, including:
- Screening for liver disease in asymptomatic patients 3
- Suggesting the underlying cause of liver disease 3
- Estimating the severity of liver disease 3
- Monitoring the efficacy of therapy 3
- Guiding further diagnostic evaluation 3
Limitations of LFTs
There are limitations to the use of LFTs, including:
- No single laboratory test or battery of tests can provide a complete estimate of liver function 3
- Abnormal LFTs may not always indicate liver disease 4
- Normal LFTs do not rule out advanced chronic liver disease, such as liver fibrosis or cirrhosis 4
Comprehensive Assessment of Liver Function
A comprehensive assessment of liver function includes: