Undetected chronic obstructive pulmonary disease and asthma in people over 50 years with persistent cough

BACKGROUND: Chronic obstructive pulmonary disease (COPD) and asthma are underdiagnosed in primary care. AIM: To determine how often COPD or asthma are present in middle-aged and older patients who consult their GP for persistent cough. DESIGN OF STUDY: A cross-sectional study in 353 patients older than 50 years, visiting their GP for persistent cough and not known to have COPD or asthma. SETTING: General practice in the Netherlands. METHOD: All participants underwent extensive diagnostic work-up, including symptoms, signs, spirometry, and body plethysmography. All results were studied by an expert panel to diagnose or exclude COPD and/or asthma. The reproducibility of the panel diagnosis was assessed by calculation of Cohen's kappa statistic in a sample of 41 participants. RESULTS: Of the 353 participants, 102 (29%, 95% confidence interval [CI] = 24 to 34%) were diagnosed with COPD. In 14 of these 102 participants, both COPD and asthma were diagnosed (4%, 95% CI = 2 to 7%). Asthma (without COPD) was diagnosed in 23 (7%, 95% CI = 4 to 10%) participants. Mean duration of cough was 93 days (median 40 days). The reproducibility of the expert panel was good (Cohen's kappa = 0.90). CONCLUSION: In patients aged over 50 years who consult their GP for persistent cough, undetected COPD or asthma is frequently present.