P300 Effect of baseline alveolar gas transfer measurement (KCO) on response to biologics in severe asthma in the UK severe asthma registry
Abstract
Introduction Alveolar gas transfer measurements are known to be raised in many patients with asthma, potentially due to ventilation-perfusion mismatch. In contrast, in the other major airways disease, COPD, alveolar gas transfer is often reduced due to emphysema. Mucus plugging in airways disease can also negatively affect gas transfer. Differences in response to biologics have been noted between patients with asthma and COPD, although they are often clinically difficult to differentiate.
Objective To assess whether alveolar gas transfer, KCO, as measured at baseline, affects response to biologics in patients in the UK Severe Asthma Registry.
Methods Patients within the UK Severe Asthma Registry with recorded KCO at baseline and data on biologic response were identified. Mean KCO was compared between those patients achieving and those not achieving a positive composite response to biologics, a ≥ 50% reduction in oral steroid requiring exacerbations and/or in maintenance oral steroids. Characteristics and outcomes were also compared between patient subgroups stratified by KCO (<70%, 70–120%, >120%).
Results Baseline KCO was reported in 3586 patients in UKSAR. 216 patients had a KCO <70%, 2919 a KCO 70–120%, and 451 a KCO >120%. Comparing subgroups, with increasing KCO there were significantly increased proportions of patients who had never smoked (KCO <70%, 31.0% never smoked; KCO 70–120%, 60.0%; KCO >120%, 67.4%; p<0.001) and who were male (KCO <70%, 34.3% male; KCO 70–120%, 36.4%; KCO >120%, 52.8%; p<0.001). There were no significant differences in eosinophil counts, exacerbations in preceding year or maintenance oral steroid use.
Data on biologic response was available in 620 patients (of whom 76% were composite responders). There was no significant difference in mean KCO between those that did or did not meet the composite response threshold (95.3% vs. 97.4%, p=0.21).
Similarly, the proportion of patients achieving a composite response was not significantly different in the subgroups stratified by baseline KCO (KCO <70%, 72.7% composite responders; KCO 70–120%, 75.9% responders; KCO >120%, 78.9% responders; p=0.81).
Conclusions Although there was a trend towards an increased composite response rate in patients with increased alveolar gas transfer measurements, alveolar gas transfer does not significantly affect biologic response.
Date
2025-11-2
Type
Article
Subject
Asthma
Collections
Citation
Pfeffer P, Brown T, Patel P, et alP300 Effect of baseline alveolar gas transfer measurement (KCO) on response to biologics in severe asthma in the UK severe asthma registryThorax 2025;80:A333-A334
Journal / Source Title
Thorax
DOI
10.1136/thorax-2025-btsabstracts.481
PMID
Publisher
BMJ Publishing Group Ltd and British Thoracic Society