A 32-year-old man from Delhi presents with jaundice, dark urine, and pale stools for 10 days. Serum bilirubin is 8.2 mg/dL (conjugated 6.1 mg/dL), ALT 1200 IU/L, AST 980 IU/L, and ALP 320 IU/L. Anti-HAV IgM is negative. Abdominal ultrasound shows normal liver echotexture with no features of cirrhosis. Which investigation is most appropriate to establish the etiology of acute hepatitis in this patient?

## Clinical Scenario Analysis The patient presents with acute hepatitis (markedly elevated transaminases, conjugated hyperbilirubinemia, clinical features of acute liver injury) with **negative Anti-HAV IgM**, ruling out Hepatitis A. ## Diagnostic Approach for Acute Viral Hepatitis **Key Point:** In acute hepatitis with negative HAV serology, the next step is to differentiate between HBV, HCV, and HEV based on epidemiological and serological clues. ### Why Anti-HBc IgM and HBsAg is Correct 1. **Anti-HBc IgM** is the most specific marker for **acute HBV infection** - Appears early in acute infection (before Anti-HBc IgG) - Remains positive for ~6 months - Differentiates acute from chronic HBV 2. **HBsAg** confirms HBV infection and helps assess: - Presence of active viral replication - Infectivity status 3. **Clinical rationale:** - India is endemic for HBV (intermediate prevalence) - Acute HBV is the most common cause of acute viral hepatitis after HAV in India - The transaminitis pattern (ALT > AST) is typical of acute viral hepatitis - Normal liver echotexture rules out cirrhosis/chronic liver disease **High-Yield:** Anti-HBc IgM + HBsAg is the gold standard for diagnosing acute HBV infection. ### Serological Markers Timeline in HBV | Marker | Acute Infection | Chronic Infection | Clinical Use | |--------|-----------------|-------------------|---------------| | **HBsAg** | Appears early (1–10 wks) | Persistent (>6 months) | Initial screening | | **Anti-HBc IgM** | Present in acute phase | Absent | **Confirms acute HBV** | | **Anti-HBc IgG** | Appears later | Persistent | Marker of past/present infection | | **HBeAg** | High viral replication | Variable | Infectivity marker | | **Anti-HBe** | Appears in recovery | May be present | Seroconversion | **Clinical Pearl:** In acute HBV, Anti-HBc IgM appears before Anti-HBc IgG and is the diagnostic hallmark during the "window period" when HBsAg is disappearing but Anti-HBs has not yet appeared. ## Why HCV RNA and Anti-HEV Are Not First-Line Here - **HCV RNA (RT-PCR):** HCV typically causes mild or asymptomatic acute infection; fulminant acute hepatitis is rare. Also requires confirmation of HCV antibody first. - **Anti-HEV IgM:** HEV is more common in pregnant women and causes severe disease in pregnancy; less common in non-pregnant adults in India. Can be checked if HBV serology is negative. **Mnemonic:** **HBIM** = **H**epatitis **B** **I**nfection **M**arker (Anti-HBc IgM for acute diagnosis).