Identifying asthma and chronic obstructive pulmonary disease in patients with persistent cough presenting to general practitioners: descriptive study.

OBJECTIVE 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. DESIGN Descriptive study. SETTING Primary healthcare centre in the Netherlands. SUBJECTS 192 patients aged 18-75 years, not known to have asthma or chronic obstructive pulmonary disease, attending their general practitioner with cough persisting for at least 2 weeks. : A diagnosis of asthma or chronic obstructive pulmonary disease was based on the recurrence of airway symptoms in the past year accompanied by spirometric measurements (including bronchodilator testing) and methacholine provocation tests. A scoring formula to estimate the probability of asthma or chronic obstructive pulmonary disease, based on history and physical examination, was generated by means of logistic regression. RESULTS 74 patients (39%) were classified as having asthma, 14 (7%) as having chronic obstructive pulmonary disease. The best formula for predicting asthma or chronic obstructive pulmonary disease used scores for three symptoms: (reported) wheeze, (reported) dyspnoea, and allergen induced symptoms, together with prolonged expiration, pack years of smoking, and female sex. Variables were scored 1 when present and 0 when absent, except for allergen induced symptoms (1.5) and number of pack years of smoking (n/25). With a cut off value of 3 on the scoring formula, 76% of the patients could be classified correctly. CONCLUSIONS 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.