Abstract
BackgroundAsthma–chronic obstructive pulmonary disease (COPD) overlap (ACO) patients experience exacerbations more frequently than those with asthma or COPD alone. Since low diffusing capacity of the lung for carbon monoxide (DLCO) is known as a strong risk factor for severe exacerbation in COPD, DLCO or a transfer coefficient of the lung for carbon monoxide (KCO) is speculated to also be associated with the risk of exacerbations in ACO.MethodsThis study was conducted as an observational cohort survey at the National Hospital Organization Fukuoka National Hospital. DLCO and KCO were measured in 94 patients aged ≥ 40 years with a confirmed diagnosis of ACO. Multivariable-adjusted hazard ratios (HRs) for the exacerbation-free rate over one year were estimated and compared across the levels of DLCO and KCO.ResultsWithin one year, 33.3% of the cohort experienced exacerbations. After adjustment for potential confounders, low KCO (< 80% per predicted) was positively associated with the incidence of exacerbation (multivariable-adjusted HR = 3.71 (95% confidence interval 1.32–10.4)). The association between low DLCO (< 80% per predicted) and exacerbations showed similar trends, although it failed to reach statistical significance (multivariable-adjusted HR = 1.31 (95% confidence interval 0.55–3.11)).ConclusionsLow KCO was a significant risk factor for exacerbations among patients with ACO. Clinicians should be aware that ACO patients with impaired KCO are at increased risk of exacerbations and that careful management in such a population is mandatory.
Highlights
Asthma–chronic obstructive pulmonary disease (COPD) overlap (ACO) patients experience exacerba‐ tions more frequently than those with asthma or COPD alone
ACO was defined as the presence of three major criteria: (i) persistent airflow limitation, that is, post-bronchodilator forced expiratory volume in 1 s to forced vital capacity < 70%; (ii) at least one feature associated with COPD; and (iii) one or more asthmatic features
Our study showed that impaired KCO % pred was a significant risk factor for exacerbation of ACO
Summary
Asthma–chronic obstructive pulmonary disease (COPD) overlap (ACO) patients experience exacerba‐ tions more frequently than those with asthma or COPD alone. Since low diffusing capacity of the lung for carbon monoxide (DLCO) is known as a strong risk factor for severe exacerbation in COPD, DLCO or a transfer coefficient of the lung for carbon monoxide (KCO) is speculated to be associated with the risk of exacerbations in ACO. The clinical characteristics of patients with coexisting asthma and chronic obstructive pulmonary disease (COPD), namely asthma–COPD overlap (ACO), have been matters of great concern for physicians [1, 2]. Assessing the influence of DLCO and KCO on ACO exacerbations could be of great benefit for improving health management for such patients
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