P96 Is long-term omalizumab therapy associated with increased sputum microbiology positivity?

Background Pseudomonas and other Gram-negative infections in chronic lung disease are associated with high levels of morbidity and mortality and are difficult to treat. Omalizumab has been available for more than 10 years and mepolizumab for the last 2 years as commonly used monoclonal antibodies in the treatment of severe asthma. Aim To evaluate a clinical suspicion of an increased prevalence of Pseudomonas spp.(and other Gram-negative bacteria) seen among our patients on long term omalizumab compared to a comparable population (those treated with mepolizumab). Methods The patient cohort was being treated at a large severe asthma service with either omalizumab (n=179) or mepolizumab (n=209). Sputum sample results from 01/01/17 to 11/02/19 on the electronic patient records for both groups were compared, along with demographic and disease severity data. Statistical analyses were performed using either Pearson’s Chi-squared test or Student’s t-test. Results Comparing the demographic features of the two treatment groups, there was no significant difference in the FEV1 (1.94L in the omalizumab group vs 2.02L, p=0.39) or the proportion of patients with evidence of bronchiectasis on CT (22.5% vs 19.8%, p=0.21). However, the mepolizumab cohort was older (52.2 vs 48.8 years old, p There were 15.8 and 7.9 sputum samples/100 patients/year positive for potentially pathogenic bacteria in the omalizumab and mepolizumab groups respectively (p Of the omalizumab patients, 3.4% and grew Gram-negative bacteria in their sputum over the study period compared to 1.4% of the mepolizumab patients. Three patients (1.7%) grew Pseudomonas spp. in the omalizumab group, compared to none in the mepolizumab group. Conclusion This retrospective study lends support to a clinical suspicion of an excess of the Gram-negative bacteria and Pseudomonas spp.in patients on long term omalizumab. The cause could be a sampling bias, with more samples being performed on omalizumab patients, longer duration of follow up in a severe asthma service, or a possible switch to an infection phenotype in patients on long term anti-IgE therapy. This clinical concern needs further evaluation in a multi-centre longitudinal real life study.