Hepatitis B core antibody （anti-HBc） is an important marker of prior HBV exposure and potential viral persistence. During acute HBV infection， anti-HBc IgM is the earliest antibody to appear shortly after HBsAg， usually lasting for 6 — 12 months， followed by anti-HBc IgG. In patients with chronic infection experiencing acute hepatitis flares， anti-HBc IgM may reappear， though typically at lower titers than in acute infection. “Isolated anti-HBc positivity” may indicate resolved/functional cure of prior HBV infection or occult HBV infection， and there is still a risk of HBV reactivation or transmission during chemotherapy， immunotherapy， blood transfusion， or organ transplantation. Therefore， accurate recognition of the clinical significance of anti-HBc is essential for comprehensive evaluation and individualized management of HBV infection.