Expected Changes in Liver Function Tests in Acute Hepatitis A
In acute hepatitis A, expect AST and ALT elevations greater than 400 IU/mL accompanied by serum bilirubin exceeding 3 mg/dL (50 μmol/L), with positive anti-HAV IgM antibody confirming the diagnosis. 1
Aminotransferase Pattern
- Both ALT and AST rise rapidly during the prodromal period, typically reaching peak levels of >400 IU/mL and often exceeding 1,000 IU/mL in symptomatic cases 1, 2
- The transaminases begin their dramatic rise before jaundice appears, peaking during the early symptomatic phase 2
- After peaking, aminotransferases decline by approximately 75% per week, normalizing within 6 months in nearly all adult patients 2
- ALT is generally higher than AST in viral hepatitis, distinguishing it from ischemic hepatitis where AST typically exceeds ALT 3
Bilirubin Elevation
- Serum bilirubin rises to levels >3 mg/dL (>50 μmol/L), which is a key diagnostic criterion when combined with elevated transaminases 1
- Bilirubin peaks later than aminotransferases and declines more slowly 2
- The period of clinical jaundice persists for less than 2 weeks in approximately 85% of cases 2
- The combination of transaminases >400 IU/mL with bilirubin >3 mg/dL helps distinguish viral hepatitis from ischemic hepatitis (where bilirubin typically remains <3 mg/dL despite massive transaminase elevation) 3
Other Liver Function Parameters
- Alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) may show mild-to-moderate elevations, but the pattern is predominantly hepatocellular rather than cholestatic 4
- Prothrombin time may be mildly prolonged in moderate cases, but severe coagulopathy is uncommon unless fulminant hepatic failure develops 5
- Serum albumin typically remains normal in acute hepatitis A, as synthetic function is preserved in self-limited disease 2
Diagnostic Confirmation
- Anti-HAV IgM antibody is the definitive serologic marker and should be ordered as part of the first-line evaluation of any acute hepatocellular injury 1, 6
- Testing should include a comprehensive viral hepatitis panel (HAV IgM, HBsAg, anti-HBc IgM, anti-HCV, HCV RNA, anti-HEV IgM/IgG) to exclude other viral etiologies 3, 6
- HAV RNA can be detected in serum but is not routinely necessary for diagnosis when anti-HAV IgM is positive 4
Severity Markers
- Peak ALT, initial LDH, peak creatinine, and peak bilirubin correlate with disease severity 5
- An ALT/LDH ratio >1.5 favors viral hepatitis over ischemic hepatitis 3
- Age is an independent risk factor for severe acute hepatitis, with older adults experiencing more severe disease 5
- Total cholesterol levels inversely correlate with severity (lower cholesterol indicates more severe disease) 5
Clinical Pitfalls to Avoid
- Do not exclude hepatitis A based on lack of travel history, as HAV is now a common cause of acute viral hepatitis in developed countries 1, 6
- Do not delay anti-HAV IgM testing; it should be part of the initial Day 0 evaluation alongside other viral serologies 6
- Recognize that fulminant hepatic failure from hepatitis A is rare but age-dependent, occurring more frequently in older adults and those with underlying chronic liver disease 1, 2
- Be aware that hepatitis A can trigger autoimmune hepatitis in susceptible individuals, manifesting as persistent or relapsing transaminase elevation after initial improvement 7
- Monitor for prolonged cholestasis (uncommon but possible), which still resolves without progression to chronic hepatitis 2