Reid index is useful in-

Ref: Textbook of pathology (Harash mohan)6th edition, page no.478 Just as there is clinical definition, there is histologic definition of chronic bronchitis by increased Reid index. Reid index is the ratio between thickness of the submucosal mucus glands (i.e. hyperophy and hyperplasia) in the cailage-containing large airways to that of the total bronchial wall . The increase in thickness can be quantitatively assessed by micrometer lens. The bronchial epithelium may show squamous metaplasia and dysplasia. There is little chronic inflammatory cell infiltrate. The non-cailage containing small airways show goblet cell hyperplasia and intraluminal and peribronchial fibrosis.