Abstract
Introduction: Asthma was the commonest co-morbid illness in patients admitted to hospital with influenza A/H1N1. Yet patients with asthma were half as likely to die or require admission to level 2 (high dependency) or level 3 (intensive) care.
Hypothesis: Asthma, rather than associated co-morbidities or treatments such as the use of steroids, is an independent factor for improved outcomes in influenza A/H1N1.
Methods: Between April 2009 and January 2010, FLU-CIN collected clinical, epidemiological and outcome data on patients with confirmed influenza A/H1N1 admitted to 75 UK hospitals.
We studied 1520 patients, of whom 480 (31.6%) were <16yrs. Asthma was the commonest co-morbid illness affecting 385 (25.3%) patients.
Findings: Patients with asthma had higher rates of dyspnoea, need for supplemental oxygen and severe respiratory distress than patients who did not have asthma but were significantly less likely to die or require level 2 or 3 care (11.2% vs. 19.8%, OR 0.51, 95% CI 0.36 to 0.72). Co-morbid illnesses were more frequent in patients with asthma (22.6% vs. 7.6%). There was no difference in the proportions with pneumonia (17.1% vs. 16.6%).
The association of asthma with less severe outcome was unaffected by age, presence of co-morbidities, in-hospital anti-viral and/or antibiotic use. Adjusting for prior use of inhaled steroid changed the association with severe outcome by over 10% (OR 0.63, 95% CI 0.42 to 0.94). Adjusting for “delayed admission >4 days” had a similar effect (OR 0.63, 95% CI 0.42 to 0.95).
Conclusion: In multivariate analysis, the combination of prior inhaled steroid use and prompt admission to hospital (≤4 days) explained the association of asthma with less severe outcome.
- © 2011 ERS