Laboratory Tests for Diagnosing Cirrhosis
The most important laboratory tests for diagnosing cirrhosis include liver function tests (ALT, AST, ALP, GGT, bilirubin), serum albumin, prothrombin time/INR, complete blood count, and assessment of liver fibrosis through non-invasive methods such as elastography.
Core Laboratory Tests for Cirrhosis Diagnosis
Liver Function and Synthetic Capacity
Liver enzymes:
- Alanine aminotransferase (ALT)
- Aspartate aminotransferase (AST)
- Alkaline phosphatase (ALP)
- Gamma-glutamyl transpeptidase (GGT)
- Bilirubin (total and direct)
Synthetic function markers:
- Serum albumin (decreased in advanced cirrhosis)
- Prothrombin time (PT)/International Normalized Ratio (INR) (prolonged in cirrhosis)
Complete Blood Count
- Platelet count (thrombocytopenia is common in cirrhosis due to portal hypertension)
- Hemoglobin/hematocrit (to assess for anemia)
- White blood cell count
Non-Invasive Assessment of Liver Fibrosis
Serum-Based Fibrosis Scores
- Aspartate transaminase to platelet ratio index (APRI)
- Fibrosis-4 (FIB-4) score
- FibroTest/FibroSure
- Non-alcoholic fatty liver fibrosis score (for NAFLD-related cirrhosis)
Imaging-Based Assessment
- Transient elastography (FibroScan) - liver stiffness ≥15 kPa typically confirms cirrhosis 1
- Standard ultrasonography - to assess liver surface nodularity, size, and signs of portal hypertension
Additional Tests Based on Clinical Context
Etiological Workup
- Viral hepatitis panel: HBsAg, HBsAb, HBcAb, HCV antibodies 2
- Iron studies: Ferritin, transferrin saturation (for hemochromatosis)
- Autoimmune markers: ANA, ASMA, AMA (for autoimmune liver disease)
- Alpha-1 antitrypsin (for alpha-1 antitrypsin deficiency)
- Ceruloplasmin (for Wilson's disease in younger patients)
Assessment of Complications
- Blood urea nitrogen (BUN) and creatinine (to assess renal function)
- Electrolytes (sodium, potassium)
- Alpha-fetoprotein (for hepatocellular carcinoma screening)
Limitations of Traditional Coagulation Tests
It's important to note that traditional coagulation tests (PT/INR, aPTT) have significant limitations in cirrhosis 2:
- These tests only partially evaluate the hemostasis system
- They neglect counterbalanced factors in cirrhosis (decreased procoagulants are often balanced by decreased anticoagulants)
- They systematically underestimate coagulation capacity in cirrhotic patients
Advanced Hemostatic Assessment
In specific situations, especially before procedures or with bleeding concerns:
- Viscoelastic testing (TEG or ROTEM) may provide a more comprehensive assessment of hemostasis than traditional tests 2
- Fibrinogen level assessment may be valuable 3
Diagnostic Paracentesis
For patients with ascites (a common complication of cirrhosis):
- Diagnostic paracentesis is recommended for all patients with new-onset ascites 2
- Initial ascitic fluid analysis should include:
- Total protein concentration
- Serum ascites albumin gradient (SAAG)
- Cell count with differential (to rule out spontaneous bacterial peritonitis)
Clinical Scoring Systems
Once cirrhosis is diagnosed, these scoring systems help assess severity:
- Child-Pugh classification - incorporates bilirubin, albumin, PT/INR, ascites, and encephalopathy 2
- Model for End-Stage Liver Disease (MELD) - uses bilirubin, creatinine, and INR 2
Common Pitfalls to Avoid
- Relying solely on liver enzymes - normal liver enzymes do not exclude cirrhosis
- Overreliance on PT/INR for bleeding risk - these tests don't accurately predict bleeding risk in cirrhosis 2
- Missing non-hepatic causes of abnormal tests - kidney dysfunction can affect multiple parameters
- Failure to assess for portal hypertension - a key determinant of prognosis and complications
By systematically evaluating these laboratory parameters alongside clinical assessment and imaging, clinicians can effectively diagnose cirrhosis, determine its etiology, assess its severity, and monitor for complications.