Out of four validated miRNAs, the authors selected miR-34a-5p, downregulated in BS-COPD compared to CS-COPD, for further analysis, and chose Notch1 (a predictive target of miR-34a-5p) for quantification in the sera of the same cohort by ELISA. Here, NOTCH1 is linked to chronic obstructive pulmonary disease.