Comparison of clinical features and outcomes for asthma-COPD overlap syndrome vs. COPD patients: a systematic review and meta-analysis.

OBJECTIVE: The aim of this study was to review evidence to determine whether "pure" chronic obstructive pulmonary disease (COPD) patients without a history of asthma differ in the clinical characteristics, severity of airflow limitation, and clinical outcomes compared to patients with Asthma-COPD Overlap Syndrome (ACOS).

MATERIALS AND METHODS: An electronic search was performed in the MEDLINE, EMBASE, SCOPUS and Web of Science databases to identify comparing the clinical characteristics and outcomes between ACOS and "pure" COPD. The included studies were subjected to meta-analysis and risk of bias assessment using ROBINS-E tool. Eleven observational studies were included.

RESULTS: The results of the meta-analysis showed increased expression of lung function parameters like forced expiration volume (FEV) at 1 sec{mean difference (MD) 2.36; 95% CI [0.05,4.66] ; p=0.004; I2= 72%} and clinical symptoms in terms of fever {Relative Risk (RR) 0.34, p<0.0001}, wheezing {RR 0.39, p<0.0001} and dyspnea {RR 0.53, p<0.0001}. The comorbidities associated with ACOS patients were similar to that found in patients with "pure" COPD. Interestingly, higher body mass index (BMI) was found in patients with ACOS (MD -0.73 95% CI [-1.06, -0.41], p<0.0001.

CONCLUSIONS: The result showed higher risk in onset of frequent acute exacerbations, severe exacerbations requiring hospitalization and higher number of exacerbations experienced per year in ACOS patients. Within the limitations of the review, ACOS can be regarded as separate entity of co-existence which is classically associated with higher BMI, worsened lung function parameters and exacerbations with a varying degree of clinical symptoms.