Initial Blood Work for Liver Function Assessment
Initial investigation for potential liver disease should include bilirubin, albumin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), and γ-glutamyltransferase (GGT), together with a full blood count if not already performed within the previous 12 months. 1, 2
Core Liver Function Panel Components
The standard liver function blood work should include:
Hepatocellular Injury Markers:
- Alanine aminotransferase (ALT)
- Aspartate aminotransferase (AST)
Cholestatic Markers:
- Alkaline phosphatase (ALP)
- γ-glutamyltransferase (GGT)
Synthetic Function Markers:
- Albumin
- Prothrombin time (PT)/International Normalized Ratio (INR)
Excretory Function:
- Total bilirubin
- Direct (conjugated) bilirubin
Complete Blood Count:
- Platelet count (important for assessing portal hypertension)
- Full blood count (if not performed in the last 12 months)
Pattern Recognition in Liver Test Abnormalities
The pattern of abnormalities can help determine the category of liver disease:
- Hepatocellular pattern: Predominant elevation of ALT/AST
- Cholestatic pattern: Predominant elevation of ALP/GGT
- Mixed pattern: Elevation of both transaminases and cholestatic enzymes
Interpretation Considerations
- The extent of liver test abnormality is not necessarily a guide to clinical significance 1
- Abnormal liver blood tests should only be interpreted after review of previous results, past medical history, and current medical condition 1
- GGT is the most sensitive test for detecting liver disease with the fewest false negatives 3
- Both AST and ALT can be normal even in the setting of cirrhosis 2
- An AST:ALT ratio >1 suggests advanced fibrosis/cirrhosis 2
Follow-up Testing for Abnormal Results
If initial liver tests are abnormal, a standard liver aetiology screen should include:
- Abdominal ultrasound scan
- Hepatitis B surface antigen
- Hepatitis C antibody (with follow-on PCR if positive)
- Autoantibody panel:
- Anti-mitochondrial antibody
- Anti-smooth muscle antibody
- Antinuclear antibody
- Serum immunoglobulins
- Iron studies:
- Serum ferritin
- Transferrin saturation
Special Considerations
- For patients with suspected NAFLD, calculate fibrosis risk scores (FIB-4 or NAFLD Fibrosis Score) 1, 2
- For marked elevations in ALT (>1000 U/L), consider viral hepatitis, drug-induced liver injury, and autoimmune hepatitis 2
- For cholestatic patterns, consider primary biliary cholangitis, primary sclerosing cholangitis, and biliary obstruction 2
Common Pitfalls to Avoid
- Relying solely on the magnitude of enzyme elevation to determine clinical significance
- Missing advanced liver disease due to normal or minimally elevated transaminases
- Failing to calculate fibrosis scores for patients with NAFLD
- Overlooking the need for viral load testing in patients who test positive for hepatitis markers
By following this systematic approach to liver function testing, clinicians can effectively screen for, diagnose, and monitor liver disease, leading to improved patient outcomes through early detection and appropriate management.