Incidence of influenza-like illness into a cohort of patients affected by chronic inflammatory rheumatism and treated with biological agents

This study aimed to evaluate the incidence of influenza-like illness (ILI), from October 2009 to May 2010, in a group of patients suffering from chronic inflammatory rheumatism and treated with biological therapies. At the end of 2009-2010 influenza season, 159 patients under biological therapies answered to a questionnaire distributed 8 months before and were deeply interviewed. The group included 69 men and 90 women (mean age 47.6); forty-nine suffering from rheumatoid arthritis, 61 with psoriatic arthritis, 32 with ankylosing spondylitis and 17 with other spondyloarthritis; 146 patients were treated with anti-TNF-α, 7 with rituximab and 6 with abatacept; 128 patients assumed DMARDs and 72 patients assumed low dose of steroids. A case of ILI was identified by anamnestic findings and according to the case definitions commonly used in Europe. Seventeen percent of the considered population reported at least one episode of ILI during the monitoring period; none of the patients during the acute influenza attack suffered particularly severe symptoms and no one was hospitalized due to complications. Despite the diversity among the considered subgroups, the statistical analysis did not show any significant difference when incidence of ILI was considered for different disease, different biological agent and different association therapy. None of the examined variables resulted statistically significant concerning the relative risk evaluation. The incidence of ILI into a cohort of 159 patients treated with biological agents during the influenza season 2009-2010 resulted higher than the value reported in a wide sample of Italian population in the same period. However, the pandemic impact was not heavy among the studied patients, considering that no important complications or hospitalizations have been reported.