SAT0341 Immune Response to Hepatitis B Virus Vaccination in Patients with Spondyloarthritis Treated with Anti-TNF Therapy VS Hemodialyzed Patients

Background Hepatitis B virus (HBV) vaccination is recommended in patients with inflammatory arthropaties on biologic treatment. Usually these patients cannot complete the vaccination schedule before starting biologic therapy. Lower immune response to HBV vaccination was observed in rheumatoid arthritis patients treated with non-biologic DMARDs compared with general populationin a study published in 2002. The effect of anti-TNF therapy (antiTNF) on humoral response to influenza vaccination in patients with inflammatory arthropaties has been assessed afterwards. In a study published in 2010 a lower response was observed in patients with spondyloarthropaties (SpA) compared to a healthy sample. Up to the present moment the inmunne response to HBV vaccination in patients with SpA treated with antiTNF has not yet been assessed. Objectives Main objective: to evaluate the effect of antiTNF therapy on immune response to HBV vaccination in SpA patients. Secondary objetives: to identify potential effect modifiers on immune response to HBV vaccination; comparison with a group of hemodialyzed patients (HD). Methods Study type: This is an observational cohort study both prospective and retrospective. Patients and procedures: SpA group: Patients with SpA treated with antiTNF. They recieved 3 doses of HBV vaccination. HD group: Patients on HD who had recieved HBV vaccination following HD schedule. Stadistic analysis Proportions for categorical variables and average ± SD (or median if appropiate) for continuous variables were calculated. Categorical variables were compared by chi-square test (applying continuity correction if necessary). T-test (or Kruskal-Wallis if appropiate) was used to compare averages. Results 30 patients in the SpA group and 19 patients in the HD group were included. 17 patients (89.5%) in the HD group showed immune response to HBV vaccination whereas only 14 patients (46.7%) in the SpA group did. Immune response to vaccination was independent of any of the variables analyzed in the SpA group. When immune response was compared between the two different doses of vaccination (including all patients both from the SpA and the HD groups), a significant statistical difference was observed (p=0.034). The proportion of 'responders' was higher if the dose recieved was 40 mcg/mL. Conclusions In our study, immune response to HBV vaccination in patients with SpA treated with antiTNF was lower than in hemodialyzed patients and general population. The proportion o