What labs should be considered in portal hypertension?

Laboratory Assessment in Portal Hypertension

In patients with portal hypertension, a comprehensive laboratory assessment should include liver function tests, complete blood count with platelets, coagulation studies, and renal function tests as these provide critical information about disease severity and complications. 1

Core Laboratory Tests for Portal Hypertension

Liver Function Tests

• Bilirubin (total and direct): Elevated levels indicate impaired liver function and are components of prognostic scores
• Aminotransferases:
  • ALT (alanine transaminase)
  • AST (aspartate aminotransferase)
  • AST/ALT ratio >1 may suggest cirrhosis
• Alkaline phosphatase: Assess for cholestatic patterns
• Albumin: Low levels indicate decreased synthetic function and are used in Child-Pugh classification
• Prothrombin time/INR: Prolongation reflects decreased synthetic function 1

Complete Blood Count

• Platelet count: Thrombocytopenia (<150,000/μL) is a surrogate marker for portal hypertension
• White blood cell count: May be low due to hypersplenism
• Mean corpuscular volume (MCV): Often elevated in alcohol-related liver disease 1

Renal Function Tests

• Blood urea nitrogen (BUN)
• Creatinine: Important prognostic marker in liver disease 1

Assessment of Portal Hypertension Severity

Non-invasive Markers and Calculations

• MELD Score: Incorporates bilirubin, creatinine, and INR
• Child-Pugh Score: Includes bilirubin, albumin, INR, ascites, and encephalopathy
• APRI (AST to Platelet Ratio Index): Sensitivity 56%, specificity 68% for clinically significant portal hypertension (CSPH) 1
• FIB-4 Score: Sensitivity 54%, specificity 73% for CSPH 1
• Platelet count/spleen diameter ratio: Low ratio suggests portal hypertension 1

Specialized Tests

• Serum-ascites albumin gradient (SAAG): If ascites is present, SAAG ≥1.1 g/dL indicates portal hypertension with 97% accuracy 2
• Ascites fluid analysis: Cell count, culture, total protein, and additional tests based on clinical suspicion 2

Etiology Assessment

Viral Hepatitis Markers

• HBsAg, HBsAb, HBcAb: To detect hepatitis B infection
• HCV antibodies: To screen for hepatitis C 1
• Viral load testing: For positive viral markers 1

Other Etiologic Tests

• Autoimmune markers: ANA, ASMA, anti-LKM
• Iron studies: Transferrin, transferrin saturation
• Alpha-1 antitrypsin
• Ceruloplasmin (in younger patients)
• Alcohol biomarkers: GGT, MCV 1

Clinical Pitfalls and Considerations

1. Platelet count alone is insufficient: While thrombocytopenia (<100,000/μL) has 78% sensitivity for CSPH, a normal platelet count does not exclude portal hypertension 1

2. Blood-based tests have limited accuracy: APRI and FIB-4 have modest performance (AUROCs of 0.64 and 0.65) compared to imaging-based assessments (AUROC 0.85 for liver stiffness measurement) 1

3. Liver enzymes may be normal: Normal liver enzymes do not exclude advanced fibrosis or portal hypertension 1

4. Coexisting etiologies: About 20% of patients with alcohol use disorder and abnormal liver tests have coexisting liver disease etiologies 1

5. Interpretation of ascites: In patients with known cirrhosis, a low SAAG (<1.1 g/dL) should be interpreted cautiously, as up to 73% may have high SAAG on repeat paracentesis 2

Complementary Non-Laboratory Assessments

While laboratory tests are essential, they should be complemented with:

• Elastography: Liver stiffness measurement (LSM) by transient elastography:

  • LSM ≤15 kPa: CSPH highly unlikely
  • LSM ≥25 kPa: CSPH likely present 1

• Imaging studies: Ultrasound with Doppler, CT, or MRI to evaluate:

  • Liver morphology
  • Splenomegaly
  • Collateral vessels
  • Ascites 1

• Endoscopy: To assess for esophagogastric varices, unless low risk based on platelets >150,000 and Fibroscan <20 kPa 1

By systematically evaluating these laboratory parameters, clinicians can effectively assess the presence, severity, and complications of portal hypertension, guiding appropriate management decisions.