Use of inhaled corticosteroids in patients with bronchiectasis and risk of acquiring Haemophilus influenzae infection: a retrospective cohort study

<bold>Introduction:</bold> Although not recommended, inhaled corticosteroids (ICS) are often used to treat patients with bronchiectasis. The aim of the study was to assess whether the use of ICS in patients with bronchiectasis is associated with a dose-dependent risk of positive airway culture with <italic>Haemophilus influenzae.</italic> <bold>Methods:</bold> The study population consists of all bronchiectasis patients followed in outpatients’ clinics in eastern Denmark during 2010 to 2018. ICS use was standardized in budesonide equivalent doses and categorized in tertiles into low (26-227mcg), moderate (230-767mcg), and high (768-5918mcg), based on accumulated dose 1 year prior to cohort entry. The risk of acquiring <italic>H. influenza</italic> is estimated by Cox proportional hazard regression model, adjusted for age, sex, oral corticosteroids, concomitant asthma and COPD. <bold>Results:</bold> A total of 9212 patients’ data was included in the study. The distribution of patients in different ICS-dose groups was as follows: no ICS(n=5441, 59.1%), low-dose ICS(n=1257, 13.7%), moderate-dose ICS(n=1262, 13.7%) and high-dose ICS(n=1252, 13.6%). 665(7.2%) patients had a lower respiratory tract culture positive for H. influenza during follow-up. Use of ICS was not associated with risk <italic>H. influenza</italic>; Hazard ratio (HR) 0.88 (95%Cl, 0.64 to 1.23, p=0.4) for low-dose ICS, HR 1.2 (95%Cl, 0.92 to 1.68, p=0.14) for moderate-dose ICS, and HR 0.98 (95%Cl, 0.70 to 1.37, p=0.9) for high-dose ICS compared to no ICS use. The IPTW analysis also confirmed these results. <bold>Conclusions:</bold> The use of ICS in patients with bronchiectasis was not associated with an increased risk of acquiring <italic>H. influenzae</italic> in the lower respiratory tract.