A 28-year-old previously healthy man presents with a 5-day history of right upper quadrant (RUQ) abdominal pain, nausea, vomiting, and subsequent jaundice, with elevated liver enzymes (hypertransaminasemia), what is the most appropriate next step in diagnosis?

Hepatitis A IgM is the Most Appropriate Next Diagnostic Test for Acute Hepatitis with Jaundice

The most appropriate next step in diagnosis for this 28-year-old man with acute onset of right upper quadrant pain, jaundice, and markedly elevated liver enzymes is Hepatitis A IgM (option B).

Clinical Presentation Analysis

This patient presents with a classic case of acute hepatitis characterized by:

• 5-day history of right upper quadrant pain
• Nausea and vomiting
• Jaundice developing 2 days after initial symptoms
• Markedly elevated transaminases (ALT 990 IU/L, AST 789 IU/L)
• Normal alkaline phosphatase (109 IU/L)

This pattern strongly suggests an acute viral hepatitis presentation rather than obstructive jaundice, drug-induced liver injury, or other causes.

Diagnostic Approach

Why Hepatitis A IgM is the Correct Choice:

1. Pattern of Liver Enzyme Elevation:

   • The patient has significant hypertransaminasemia (ALT 990 IU/L, AST 789 IU/L) with normal alkaline phosphatase
   • This pattern is typical of acute hepatocellular injury rather than biliary obstruction 1
   • The AST:ALT ratio is <1, which is commonly seen in acute viral hepatitis 2

2. Clinical Timeline:

   • The 5-day history with progression to jaundice is consistent with acute viral hepatitis
   • Hepatitis A is one of the most common causes of acute viral hepatitis presenting with these symptoms 3

3. Demographic Considerations:

   • In a previously healthy young adult with no history of alcohol or drug use, infectious causes are the most likely etiology
   • Hepatitis A is a common cause of acute hepatitis in this age group 2

Why Other Options Are Less Appropriate:

• Hepatitis A IgG (Option A): Tests for past infection/immunity, not acute infection
• Hepatitis B antigen (Option C): While reasonable to test, Hepatitis A IgM should be tested first in this clinical presentation
• Hepatitis C antibodies (Option D): Hepatitis C rarely presents as acute hepatitis with jaundice; it typically causes a more indolent course 2

Differential Diagnosis

1. Acute Viral Hepatitis:

   • Hepatitis A, B, and E are the most common causes of acute viral hepatitis with jaundice 1, 2
   • Other viral causes include CMV and EBV 1, 4

2. Autoimmune Hepatitis:

   • Can present acutely with similar symptoms and laboratory findings
   • More common in females but can occur in males 1, 5
   • Testing would be considered if viral markers are negative

3. Drug-Induced Liver Injury:

   • Patient has no reported drug use, making this less likely 6
   • Would be considered if viral markers are negative

4. Wilson Disease:

   • Should be considered in young patients with acute liver failure
   • Usually has low alkaline phosphatase and AST:ALT ratio >2 1

Recommended Diagnostic Algorithm

1. First-line testing: Hepatitis A IgM (to diagnose acute HAV infection)
2. If negative, proceed with:
   • Hepatitis B surface antigen and core IgM
   • Hepatitis E IgM (especially with travel history)
   • Autoimmune markers (ANA, ASMA, immunoglobulin levels)
   • Drug toxicity screen
   • Consider Wilson disease testing in patients under 40 years 1

Important Clinical Considerations

• The normal alkaline phosphatase with markedly elevated transaminases points away from biliary obstruction and toward hepatocellular injury 1
• Acute viral hepatitis can progress to acute liver failure, requiring close monitoring of mental status and coagulation parameters 1
• If initial viral markers are negative and no improvement occurs, liver biopsy may be necessary to establish diagnosis 1

In this clinical scenario, testing for Hepatitis A IgM is the most appropriate initial diagnostic step given the acute presentation, pattern of liver enzyme elevation, and absence of other risk factors.