Characteristics Distinguish Asthma-COPD From Pure Asthma or COPD

Patients with asthma-chronic obstructive pulmonary disease (COPD) overlap have distinct features compared with patients with asthma or COPD alone, according to a recent study.

Junjie Peng, of West China School of Medicine at Sichuan University, and colleagues conducted the study to evaluate the diagnostic value of indicators for asthma-COPD overlap.

They performed the research because “some clinical indicators have been reported to be useful in differentiating asthma-chronic obstructive pulmonary disease overlap from pure asthma/COPD, but the results were inconsistent,” according to the authors.

The investigators searched the PubMed, EMBASE, Ovid, and Web of Science databases and found 48 studies eligible for inclusion in the analysis.

Patients with asthma-COPD overlap had lower predicted percentages of forced expiratory volume in the first second than patients with asthma alone (standardized mean difference [SMD], −1.09; 95% CI, −1.3 to −0.87). Patients with asthma-COPD overlap also had lower predicted percentages of diffusion lung capacity for carbon monoxide (SMD, −0.83; 95% CI, −1.24 to −0.42) and fractional exhaled nitric oxide (SMD, −0.23; 95% CI, −0.36 to −0.11) than patients with asthma alone. However, patients with asthma-COPD overlap had higher levels of induced sputum neutrophil (SMD, 0.51; 95% CI, 0.21 to 0.81) and circulating YKL-40 (SMD, 0.96; 95% CI, 0.27 to 1.64) than patients with asthma alone.

Patients with asthma-COPD overlap had higher predicted percentages of forced expiratory volume in the first second (SMD, 0.15; 95% CI, 0.05 to 0.26) and higher predicted percentages of diffusion lung capacity for carbon monoxide (SMD, 0.38; 95% CI, 0.16 to 0.6) than patients with COPD alone. Those with asthma-COPD overlap also had higher levels of fractional exhaled nitric oxide (SMD, 0.59; 95% CI, 0.40 to 0.78), serum total immunoglobulin (Ig) E (SMD, 0.42; 95% CI, 0.1 to 0.75), blood eosinophils (SMD, 0.44; 95% CI, 0.29 to 0.59), and induced sputum eosinophil (SMD, 0.62; 95% CI, 0.42 to 0.83) than patients with COPD alone. However, patients with asthma-COPD overlap had lower levels of induced sputum neutrophil (SMD, −0.48; 95% CI, −0.7 to −0.27) and circulating YKL-40 (SMD, −1.09; 95% CI, −1.92 to −0.26) than patients with COPD alone.

“Compared with pure asthma/COPD, patients [with asthma-COPD overlap] have different levels of [predicted percentages of forced expiratory volume in the first second], [predicted percentages of diffusion lung capacity for carbon monoxide], [fractional exhaled nitric oxide], serum total IgE, blood eosinophil, induced sputum eosinophil/neutrophil, and circulating YKL-40, which could be helpful to establish a clinical diagnosis of [asthma-COPD overlap],” the researchers concluded.

Peng J, Wang M, Wu Y, Shen Y, Chen L. Clinical indicators for asthma-COPD overlap: a systematic review and meta-analysis. Int J Chron Obstruct Pulmon Dis. 2022;17:2567-2575. doi:10.2147/COPD.S374079