TABLE 4.

Biomarker role of circRNAs in COPD.

CircRNAs	Expression level	Study size	Biomarker role	Biomarker type	Refs
Circ_0001859	↓ in serum of COPD and AE-COPD patients	Healthy n = 28	Higher specificity and sensitivity in predicting COPD and AE-COPD, and correlated with FEV1% predicted	Diagnostic and prognostic	Chen et al. (2020)
		COPD n = 38
		AE-COPD n = 24
Circ_0040929	↑ in the blood of smokers with and without COPD	Non-smokers n = 22	Circ_0040929 expression was higher in COPD compared to smokers and non-smokers	Diagnosis	Miao et al. (2022)
		Smokers n = 22
		COPD n = 22