BMJ : British medical journal
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To determine the prevalence of asthma and chronic obstructive pulmonary disease in patients not known to have these disorders, who present in general practice with persistent cough, and to ascertain criteria to help general practitioners in diagnosis. ⋯ About half of patients with persistent cough who present to a general practitioner have asthma or chronic obstructive pulmonary disease. With a simple formula based on three symptoms and prolonged expiration, pack years of smoking, and female sex, most patients may be identified correctly in general practice.