Hepatitis B reactivation in patients with chronic hepatitis C undergoing anti-viral therapy with an interferon-free regimen M.-C. Londo~ no* , S. Lens*, Z. Mari~ no*, M. Bonacci*, X. Ariza*, T. Broquetas † , A. Pla*, C. Bartres*, M. V. Adriani*, S. Rodrıguez-Tajes*, J. Costa ‡ , J. A. Carri on † , S. Perez-del-Pulgar* & X. Forns* *Liver Unit, IDIBAPS and CIBEREHD, Hospital Clınic Barcelona, Barcelona, Spain. † Liver Unit, Gastroenterology Department, Hospital del Mar, IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain. ‡ Microbiology Department, Hospital Clınic Barcelona, Barcelona, Spain. Correspondence to: Dr M.-C. Londo~ no, Liver Unit, Hospital Clınic Barcelona, Calle Villarroel 170, 08036 Barcelona, Spain. E-mail: mlondono@clinic.ub.es Publication data Submitted 3 August 2016 First decision 31 August 2016 Resubmitted 10 November 2016 Resubmitted 16 December 2016 Accepted 23 January 2017 EV Pub Online 16 February 2017 The Handling Editor for this article was Professor Geoffrey Dusheiko, and it was accepted for publication after full peer-review. SUMMARY Background A few cases of hepatitis B virus (HBV) reactivation during anti-viral ther- apy against hepatitis C (HCV) have been reported. However, the informa- tion regarding the real impact of this phenomenon is scarce. Aim To evaluate the risk of HBV reactivation during anti-viral therapy against HCV with an interferon-free regimen with direct-acting anti-virals (DAAs). Methods Observational and prospective study of 352 patients receiving DAAs ther- apy between September 2015 and May 2016. HBV-DNA and ALT levels were monitored at baseline, at week 4 of anti-viral therapy, at end of treat- ment and 12 weeks after treatment discontinuation in patients with HBV surface antigen (HBsAg) positive or HBV core antibody (anti-HBc) positive before starting anti-viral therapy. Results Ten (2.8%) and 64 (18%) patients were HBsAg and anti-HBc positive at baseline, respectively. Five (50%) of 10 HBsAg positive and one (1.6%) of 64 anti-HBc positive patients presented HBV virological reactivation (>1log increase in HBV-DNA levels). None of these patients presented clinical reactivation (increase in ALT levels). Conclusions HBV virological reactivation is frequent in HBsAg+ patients receiving anti- viral therapy against HCV. However, HBV-DNA elevations were modest (<20 000 IU/mL) and without clinical impact (no ALT elevation). Aliment Pharmacol Ther 2017; 45: 1156–1161 ª 2017 John Wiley & Sons Ltd doi:10.1111/apt.13985 1156 Alimentary Pharmacology and Therapeutics