There a several potential interpretations of an isolated anti-HBc positive result (with a negative HBsAg and negative anti-HBs). Additional evaluation of the patient’s immune status and risk history is needed. A 2011–2018 national survey found the prevalence of isolated positive anti-HBc is about 0.8%. The total anti-HBc tests are very accurate, at about 99.8% specificity; however, if a person has no risk factors for hepatitis B, the result may be a false positive. Other possibilities include: a past resolved infection; an occult infection (HBV DNA is detectable but surface antigen is not detected); an early infection tested during the brief period of time before anti-HBs antibodies are detectable; or, an infection with a hepatitis B virus with a mutant surface antigen not detectable by standard tests. Depending upon the circumstances, consultation with a specialist may be helpful.
Additional resources for the evaluation of isolated anti-HBc antibody results are available from the University of Washington: www.hepatitisb.uw.edu/go/screening-diagnosis/diagnosis-hbv/ core-concept/all and from CDC: www.cdc.gov/hepatitis/hbv/interpretationOfHepBSerologicResults.htm.