Significance of anti-HBc alone serological status in clinical practice.

Serum samples identified as positive for total anti-HBc, but negative for both HBsAg and anti-HBs, are referred to as anti-HBc alone. This serological response is compatible with acute, resolved, and chronic hepatitis B virus (HBV)infection but might also signify occult HBV infection. Once the anti-HBc alone pattern is detected, false-positive reactivity should be ruled out and further analyses can resolve the clinical status of the donor. The identification of anti-HBc positivity in the absence of HBsAg in organ transplant donors and in candidate patients for chemotherapy and immunosuppressive therapy requires further investigation because of the risk of HBV reactivation. False-positive detection, acute infection during the window phase, and resolved or chronic HBV infection are all possible and only distinguishable if the additional assays are done and measures of liver damage are taken into account. Measurement of serum anti-HBs responses after the administration of HBV vaccination can be useful to distinguish this serological profile. In view of the low risk of HBV reactivation in anti-HBc alone patients who are candidates for immunosuppressive treatment, such patients might not require pre-emptive antiviral therapy, but should be followed up on a monthly basis for alanine aminotransferase followed by quantitative HBV DNA testing in those with alanine aminotransferase increase. According to specific guidelines, nucleoside analogue prophylaxis is recommended in anti-HBc-positive liver allograft recipients and anti-HBc alone individuals who receive chemotherapy or biological therapy and should be continued for 6-12 months after discontinuation of such immunosuppressive therapies to protect against HBV reactivation.