Appropriate Blood Tests for Suspected Acute Liver Injury

     The liver plays a crucial role in maintaining homeostasis, and when acute injury occurs, a thorough evaluation is necessary to determine the extent of damage and underlying cause. Blood tests are essential in assessing liver function, hepatocellular integrity, and potential viral infections. The primary tests ordered for suspected acute liver injury include liver function tests (LFTs), coagulation studies, and viral serologies. Liver function tests provide insight into hepatocyte integrity and bile excretion. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are key markers of hepatocellular damage, often rising significantly in acute injury. In cases of acute hepatitis A virus (HAV) infection, ALT levels can exceed 1000 U/L, with AST also elevated but typically lower than ALT. Alkaline phosphatase (ALP) and gamma-glutamyl transferase (GGT) assess biliary function, with ALP being mildly elevated in HAV cases. Additionally, total and direct bilirubin levels are crucial in evaluating bile processing and excretion, often presenting as hyperbilirubinemia in acute HAV, which correlates with jaundice. Albumin levels, while generally normal in acute liver injury, may decrease in severe hepatic dysfunction.

      Coagulation studies, including prothrombin time (PT) and international normalized ratio (INR), assess the liver’s synthetic function. Since the liver produces clotting factors, significant hepatic impairment can prolong PT/INR, indicating a decline in liver function. In mild cases of HAV, coagulation parameters remain normal, but in severe cases, PT may be prolonged. To confirm HAV infection, viral serologies are essential. The presence of HAV IgM antibodies indicates a recent or active infection, differentiating it from past exposure or vaccination. HAV IgG antibodies, on the other hand, suggest immunity from prior infection or immunization. The hallmark laboratory findings in acute HAV include markedly elevated ALT and AST, mild increases in ALP, hyperbilirubinemia, and a positive HAV IgM test, confirming acute infection.

References

Jameson, J. L., Fauci, A. S., Kasper, D. L., Hauser, S. L., Longo, D. L., & Loscalzo, J. (2022). Harrison’s Principles of Internal Medicine (21st ed.). McGraw-Hill Education.

Lee, W. M. (2020). Acute liver failure. The New England Journal of Medicine, 382(22), 2137-2145. https://doi.org/10.1056/NEJMra1917038

Schuppan, D., & Afdhal, N. H. (2021). Liver cirrhosis. The Lancet, 398(10308), 1359-1371. https://doi.org/10.1016/S0140-6736(21)01374-X