Background Tumor necrosis factor inhibitors (TNFi) are being widely used for treatment of ankylosing spondylitis (AS). It is known to increase the risk of hepatitis B virus (HBV) reactivation in hepatitis B surface antigen (HBsAg)-positive patients and possibly also in patients with occult HBV infection (HBsAg-negative/hepatitis B core antibody (HBcAb)-positve).

Objectives The aim of this study was to evaluate the effects of TNFi therapy on HBV reactivation in AS patients with occult HBV infection.

Methods AS patients treated with TNFi at our institution were retrospectively reviewed. Clinical datas before and after using TNFi including 3 serologic markers for HBV: HBsAg, HBcAb and hepatitis B surface antibody (HBsAb), type and duration of TNFi, and liver function tests. Definite HBV reactivation was defined as reappearance of HBsAg in a previously HBsAb-negative individual and possible HBV reactivation was defined as serum alanine aminotransaminase (ALT) elevation (>2 times upper normal limit) in patients with occult HBV infection.

Results A total 295 of AS patients on TNFi therapy were assessed excluding 7 (2.4%) patients who were HBsAg-positive. Fifty-seven (19.8%) patients who were HBcAb-positive (occult HBV infection) and 231 (80.2%) patients who were HBcAb-negative were analyzed. The mean age of patients with occult HBV infection was 48.96 ± 11.26 years, which was significantly higher than patients who were HBcAb-negative (35.86 ± 9.61). Duration of TNFi therapy, type and number of TNFi used, proportion of patients with abnormal liver function test, and HLA-B27 positivity did not differ significantly between the 2 groups. None of the patients showed definite HBV reactivation during TNFi therapy. However, 5 (2.2%) HBcAb-negative patients converted to HBcAb-positive after TNFi therapy. Their follow up ALT levels remained within normal ranges. Two (3.5%) of the 57 patients with occult HBV infection showed possible HBV reactivation with elevation in ALT levels. One of these patients had also on methotrexate and liver function normalized with discontinuation of methotrexate.

Conclusions TNFi therapy was safe in AS patients with occult HBV infection. Nevertheless, close monitoring is necessary for detection of HBV reactivation in patients with occult HBV infection.

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Disclosure of Interest None declared