What additional labs are recommended for a patient with hyperbilirubinemia, anemia, and elevated AST?

Additional Laboratory Tests for a Patient with Elevated Bilirubin, Low RBC/Hematocrit, and Elevated AST

For a 79-year-old patient with elevated bilirubin, low RBC/hematocrit, and elevated AST, a complete hepatic and hematologic workup should be performed, including direct/conjugated bilirubin, complete liver panel, coagulation studies, and specific tests to evaluate for hemolysis. 1, 2

Initial Laboratory Evaluation

Comprehensive Liver Panel

• Direct/conjugated bilirubin - Essential to differentiate between conjugated and unconjugated hyperbilirubinemia 1
• Complete liver enzymes:
  • ALT (already elevated AST noted)
  • Alkaline phosphatase (ALP)
  • Gamma-glutamyl transferase (GGT) 3, 2
• Liver synthetic function:
  • Albumin
  • Prothrombin time (PT)/INR 1, 4

Hematologic Workup

• Complete blood count with differential (already noted low RBC/hematocrit)
• Reticulocyte count - To assess bone marrow response to anemia
• Peripheral blood smear - To evaluate for hemolysis, abnormal cell morphology
• Hemolysis panel:
  • Lactate dehydrogenase (LDH)
  • Haptoglobin
  • Direct antiglobulin test (DAT/Coombs test) 2

Second-Line Testing

Viral Hepatitis Screening

• Hepatitis B surface antigen (HBsAg)
• Hepatitis B core antibody (anti-HBc)
• Hepatitis C antibody (anti-HCV) 2

Iron Studies

• Ferritin
• Serum iron
• Total iron binding capacity (TIBC)
• Transferrin saturation 2

Autoimmune Markers

• Antinuclear antibody (ANA)
• Anti-smooth muscle antibody (ASMA)
• Anti-mitochondrial antibody (AMA) 3, 2

Imaging Studies

• Abdominal ultrasound - First-line imaging to evaluate for:

  • Biliary obstruction
  • Liver parenchymal disease
  • Masses
  • Gallstones 1

• Consider MRCP or CT with contrast if biliary obstruction is suspected based on ultrasound findings 1

Interpretation and Decision-Making

Pattern Recognition

1. Predominantly conjugated hyperbilirubinemia (direct bilirubin >35% of total):

   • Suggests hepatocellular damage, biliary obstruction, or drug-induced liver injury 1

2. Predominantly unconjugated hyperbilirubinemia (direct bilirubin <20-30% of total):

   • Suggests hemolysis, Gilbert's syndrome, or ineffective erythropoiesis 1

3. Combined anemia and liver test abnormalities:

   • Consider hemolytic anemia with secondary liver involvement
   • Evaluate for malignancy with liver metastases
   • Consider alcohol-related liver disease 5, 2

Special Considerations for the Elderly

• Drug-induced liver injury is more common in older adults
• Malignancy (primary or metastatic) must be considered in this age group
• Vascular causes (ischemic hepatitis, Budd-Chiari syndrome) should be evaluated 2

Follow-up Testing

• If initial workup is inconclusive, consider:
  • Liver biopsy
  • Specialized imaging (MRI liver, CT with contrast)
  • Consultation with hepatology and/or hematology 1, 2

The combination of elevated bilirubin, low RBC/hematocrit, and elevated AST suggests either a primary liver disease with secondary anemia or a hematologic disorder with secondary liver involvement. A systematic approach with appropriate laboratory testing will help determine the underlying etiology and guide appropriate management.