When serology misleads: cross-reactivity in acute hepatitis

Acute viral hepatitis (AVH) caused by hepatitis A virus (HAV), hepatitis E virus (HEV), Epstein-Barr virus (EBV), and cytomegalovirus (CMV) often presents with similar clinical and biochemical features. However, serological cross-reactivity among these viruses poses significant diagnostic challenges, potentially leading to misclassification, inappropriate management, and unreliable epidemiological data. To review the immunological mechanisms contributing to serological cross-reactivity in AVH and highlight the diagnostic and clinical implications, with a focus on the importance of molecular confirmation. A structured literature review was conducted using the PubMed, EMBASE, Scopus, and Web of Science databases. Keywords included terms related to cross-reactivity, acute hepatitis, serological testing, molecular diagnostics, and specific viral agents. Peer-reviewed studies published in English up to 2025 were included. Cross-reactivity in AVH is primarily driven by polyclonal B-cell activation, antibody polyreactivity, and T-cell receptor cross-specificity. Studies report that up to 33.3% of anti-HEV IgM-positive samples also test positive for EBV or CMV IgM, despite negative PCR confirmation. This overlap is particularly problematic in immunocompromised individuals and pregnant women, where accurate pathogen identification is critical. While PCR offers superior specificity and sensitivity, its implementation is limited by cost and accessibility in low-resource settings. Serological cross-reactivity in acute hepatitis significantly impacts diagnostic precision and clinical decision-making. Incorporating molecular testing, especially PCR, into diagnostic workflows is essential to ensure accurate diagnosis, particularly in high-risk populations.