Reid index is useful in the diagnosis of:

Ref: Chapter 15. The Lung: page: 688: Robbins and Cot ran Pathologic Basis of Disease: 8th editionExplanation:* The Reid index is ratio of the thickness of the mucous gland layer to the thickness of wall between the epithelium and cartilage.The normal Reid index is 0.4 and it is increased in chronic bronchitis, usually in proportion to the severity and duration of the disease.Asthma is associated with type 1 hypersensitivity reaction and shows Curschmann spirals and Charcot -Leyden crystals in the mucous plugs.Bronchiectasis is associated with Kartagener syndrome: Bronchiectasis, infertility, sinusitis and situs inversus.Emphysema is commonly associated with alpha-1 antitrypsin deficiency resulting in protease-anti protease imbalance.