Risk factors for bronchiectasis in patients with chronic obstructive pulmonary disease: a systematic review and meta-analysis.

The risk factors of bronchiectasis in patients with chronic obstructive pulmonary disease have not yet been established. This systematic review and meta-analysis aimed to investigate and identify potential risk factors for patients with chronic obstructive pulmonary disease accompanied by bronchiectasis. We reviewed eight electronic journal databases from their inception to November 2019 for observational studies with no language restrictions. The Newcastle-Ottawa Scale was applied to evaluate the quality of the literature. Binary variables were pooled using odds ratios and continuous variables using the standardized mean difference with 95% confidence intervals. The confidence of evidence was assessed according to the grading of the recommendations assessment, development, and evaluation method. Eight case-control studies met the inclusion criteria. Tuberculosis history, smoking history, hospitalization stays, admissions in the past year, and duration of symptoms were considered risk factors. In addition, the ratio between the forced expiratory volume in 1s and forced vital capacity, the percentage of forced expiratory volume in 1s, the forced expiratory volume in 1s as a percentage of the predicted value, purulent sputum, purulent mucus sputum, positive sputum culture, Pseudomonas aeruginosa infection, arterial oxygen pressure, daily dyspnea, C-reactive protein, leukocytes, and the percentage of neutrophils were found to be closely related to bronchiectasis. However, these were not considered risk factors. The evidence of all outcomes was judged as "low" or "very low." Additional prospective studies are required to elucidate the underlying risk factors and identify effective preventive interventions.