Clinical Indicators for Asthma-COPD Overlap: A Systematic Review and Meta-Analysis.

BACKGROUND

Some clinical indicators have been reported to be useful in differentiating asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) from pure asthma/COPD, but the results were inconsistent. This study aims to evaluate the diagnostic value of these indicators for ACO.

METHODS

Databases of PubMed, EMBASE, Ovid and Web of Science were retrieved. Pooled standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated in random-effects models.

RESULTS

48 eligible studies were included. The pooled results indicated, compared with pure asthma, ACO patients had lower levels of forced expiratory volume in the first second (FEV)% predicted (pred) (SMD=-1.09, 95% CI -1.3 to -0.87), diffusion lung capacity for carbon monoxide (DLCO)% pred (SMD=-0.83, 95% CI -1.24 to -0.42), fractional exhaled nitric oxide (FeNO) (SMD=-0.23, 95% CI -0.36 to -0.11), and higher levels of induced sputum neutrophil (SMD = 0.51, 95% CI 0.21 to 0.81), circulating YKL-40 (SMD = 0.96, 95% CI 0.27 to 1.64). However, relative to COPD alone, ACO patients had higher levels of FEV% pred (SMD = 0.15, 95% CI 0.05 to 0.26), DLCO% pred (SMD = 0.38, 95% CI 0.16 to 0.6), FeNO (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 eosinophil (SMD = 0.44, 95% CI 0.29 to 0.59), induced sputum eosinophil (SMD = 0.62, 95% CI 0.42 to 0.83), and lower levels of induced sputum neutrophil (SMD=-0.48, 95% CI -0.7 to -0.27), circulating YKL-40 (SMD=-1.09, 95% CI -1.92 to -0.26).

CONCLUSION

Compared with pure asthma/COPD, ACO patients have different levels of FEV% pred, DLCO% pred, FeNO, serum total IgE, blood eosinophil, induced sputum eosinophil/neutrophil, and circulating YKL-40, which could be helpful to establish a clinical diagnosis of ACO.