THRB and chronic obstructive pulmonary disease: A population-based study employing CT or microCT quantification found that compared to controls, individuals with pre-COPD and those across all GOLD grades had a significant reduction in the number of transitional bronchioles (TrB)/ml and terminal bronchioles (TB)/ml.53 Additionally, TrB and TB had fewer alveolar attachment points, with no differences observed between pre-COPD and established COPD groups [53].