Laboratory diagnosis of acute hepatitis A – Choose the most appropriate method for confirming recent HAV infection.

Introduction:
Accurate diagnosis of acute hepatitis A virus (HAV) infection is essential for clinical management and public health responses. While liver enzymes reflect hepatocellular injury, serologic tests identify etiology. This question evaluates your ability to select the standard confirmatory test for acute HAV infection.

Given Data / Assumptions:

• Acute HAV typically presents with abrupt hepatitis and cholestatic features.
• Serology for anti-HAV IgM is the routine marker of recent infection.
• Advanced methods (e.g., immunoelectron microscopy, PCR) are not standard for routine diagnosis.

Concept / Approach:
Differentiate between nonspecific markers of liver injury (AST/ALT) and pathogen-specific assays. Identify which test is widely used, rapid, and reliable to confirm recent HAV: anti-HAV IgM by ELISA, which appears early and declines over months, distinguishing it from anti-HAV IgG indicating past exposure or vaccination.

Step-by-Step Solution:
Step 1: Recognize that elevated AST/ALT only indicate hepatitis, not its cause.Step 2: Note that immunoelectron microscopy is research-level and impractical for routine clinical labs.Step 3: Identify anti-HAV IgM ELISA as the standard confirmatory test for acute infection.Step 4: Consider that PCR is useful in specialized contexts but is not the frontline confirmatory tool in many settings.

Verification / Alternative check:
Guidelines and textbooks endorse anti-HAV IgM as the primary diagnostic marker for recent HAV, with anti-HAV IgG reflecting immunity from past infection or vaccination.

Why Other Options Are Wrong:

• AST/ALT alone: nonspecific for etiology.
• Immunoelectron microscopy: not routine; low practicality.
• Both (a) and (b): still lacks a standard serologic confirmation.
• PCR only during convalescence: timing and availability issues; not standard first-line confirmation.

Common Pitfalls:
Equating biochemical hepatitis with a specific viral diagnosis; overlooking the diagnostic window and interpretation of IgM vs IgG.

Final Answer:
Detection of anti-HAV IgM by ELISA.