Changes in Anti-HBc Positivity and Antibody Loss in Immunocompromised Patients: An Eight-Year Hospital-Based Analysis From a Tertiary Center in Turkey.

This study aimed to evaluate the prevalence of anti-HBc seropositivity and examine the longitudinal changes in anti-HBc IgG S/CO reactivity, with particular focus on seroreversion (loss of anti-HBc antibodies) in immunocompromised patients by correlating laboratory data with clinical history. In this retrospective study (January 2017 and June 2024), serum samples from a tertiary care hospital were tested for hepatitis B serological markers, using chemiluminescent microparticle immunoassay (CMIA). Patients with ≥ 3 anti-HBc IgG measurements were evaluated for longitudinal monitoring of antibody dynamics. Medical records were reviewed for chronic HBV infection, co-morbidities, and anti-HBc loss in immunosuppressed patients. A total of 35,017 clinical samples from 27,758 participants were analysed. In this hospital-based cohort, the anti-HBc IgG seropositivity rate was 32.0%. Seropositive individuals were older than seronegatives (p < 0.001). Longitudinal analyses was performed on 1397 patients with ≥ 3 IgG measurements; consistently 434 remained reactive and 963 remained negative. Linear mixed-effects analysis showed a significant decline over time (F(1,1679) = 33.65; p < 0.001). Among immunosuppressed patients, 94 initially reactive cases were evaluated; permanent loss occurred in 80.9%. Seroreversion rates were 66.7% in rheumatology, 85.2% in hematology, 100% in oncology, and 69.2% in other departments; massive immunosuppressive cohort (hematology/oncology) had a higher likelihood of seroreversion in an unadjusted, exploratory comparison (OR 3.27; p = 0.04). This study demonstrates time-dependent decline in anti-HBc IgG S/CO reactivity. Seroreversion is common in immunocompromised patients. As anti-HBc reflects past exposure rather than active infection, its loss or negativity in immunosuppressed patients-including seronegative occult HBV infection-means serology alone may give false reassurance. Combined HBsAg/anti-HBc serology with HBV DNA testing is therefore recommended to detect occult infection and assess reactivation risk in this high-risk group.