Size Matters! Anti-HBs Titer and HBV Reactivation During Anti-TNF Therapy

Background and Aims We and others have previously described that hepatitis B surface antibody (anti-HBs) seems to protect against clinically significant HBV reactivation in cohort studies of patients undergoing anti-tumor necrosis factor (TNF) therapy. However, there were too few cases of HBV reactivation within cohort studies to assess the role of anti-HBs titer on reactivation. The purpose of this study was to systematically review the correlation between anti-HBs titer and the degree of clinically relevant HBV reactivation in patients undergoing anti-TNF therapy. Methods and Results We systemically reviewed all studies discussing anti-TNF therapy in patients with resolved HBV infection, defined as hepatitis surface antigen (HBsAg) negative and hepatitis B core antibody (anti-HBc) positive. We identified a total of 48 cases of reactivation from 5 cohort studies and 10 case reports or case series; 21 were anti-HBs negative, 7 were only reported as anti-HBs positive, 16 were anti-HBs positive with titer below 100, and 4 were anti-HBs positive with titer above 100. HBsAg sero-reversion was dominantly seen in patients with negative, low and/or declining anti-HBs titers. There was a significant trend toward less clinically relevant form of reactivation with increase in baseline anti-HBs titer ( p = 0.022). Conclusion Anti-HBs titers greater than 100 iU/L protect against clinically relevant HBV reactivation, while patients with low anti-HBs titers or negative anti-HBs had more clinically relevant HBV reactivation and higher rates of HBsAg sero-reversion. This suggests the importance of baseline quantitative anti-HBs prior to starting anti-TNF therapy and consideration vaccination for boosting anti-HBs titers prior to and/or during therapy.