Detection of antibodies to hepatitis B core antigen using the Abbott ARCHITECT® anti-HBc assay: Analysis of borderline reactive sera

Routine use of the automated chemiluminescent microparticle immunoassay Abbott ARCHITECT® anti-HBc for diagnosis of hepatitis B is limited in case of borderline reactive sera with low signal close to the cut-off index. In order to determine the significance of anti-HBc detection when borderline reactivity occurs using the ARCHITECT® anti-HBc assay, a comparative study was designed. 3540 serum samples collected over a 2-month period in the hospital of Nice were examined for markers of HBV infection (HBsAg, anti-HBs and anti-HBc). One hundred seven samples with sufficient volume and with borderline reactivity by the ARCHITECT® assay were tested by two other anti-HBc assays, a microparticle enzyme immunoassay (MEIA, AxSYM® Core™, Abbott Laboratories, IL, USA) and an enzyme linked fluorescent assay (ELFA, VIDAS® Anti-HBc Total II, bioMérieux, Lyon, France). Only 46 samples were confirmed by the AxSYM® and the VIDAS® assays. Additional serological information linked to patient history showed that the remaining samples (61) were false positives (11), had low titer of anti-HBc antibodies (13), or were inconclusive (37). This comparative study highlighted the existence of a grey zone around the cut-off index. Confirmative results through a different immunoassay are needed to confirm the diagnosis of HBV on borderline reactive sera using the ARCHITECT® anti-HBc assay.