Reid index refers to the relative thickness of submucosal mucus glands; which statement describes an increased Reid index?

• A. Enlargement of submucosal mucous glands
• B. Increase goblet cells
• C. Increase cartilage
• D. Thickening of smooth muscle

Answer: (A)

Reid index measures the thickness of submucosal mucus glands relative to the thickness of the surrounding bronchial wall. An increased index means the submucosal gland layer has hypertrophied or hyperplastic, elevating the ratio and signaling more mucus production, as seen in chronic bronchitis. Therefore, enlargement of submucosal mucous glands best describes an increased Reid index. Goblet cell increases involve the epithelium rather than the submucosal glands, and changes in cartilage or smooth muscle reflect other structural alterations, not the gland thickness measured by this index. Normal Reid index is about 0.4; values above roughly 0.5 indicate mucous gland hypertrophy.