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 (120%). Results Baseline KCO was reported in 3586 patients in UKSAR. 216 patients had a KCO 120%. Comparing subgroups, with increasing KCO there were significantly increased proportions of patients who had never smoked (KCO 120%, 67.4%; p120%, 67.4%; p120%, 52.8%; p120%, 52.8%; p120%, 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.