External validation of a COPD diagnostic questionnaire.

The aim of the present study was to determine the external validity of a recently developed questionnaire for the identification of patients at increased risk of airflow limitation in smokers from the general population in the provinces of Dutch and Belgian Limburg (regions surrounding Maastricht, the Netherlands). As part of a study on the early detection of airflow limitation and subsequent smoking cessation treatment (International Standard Randomised Controlled Trial Number: 64481813), the recently developed chronic obstructive pulmonary disease (COPD) diagnostic questionnaire was used in current smokers aged 40-70 yrs, with a smoking history of >or=10 pack-yrs, who reported one or more respiratory symptom (cough, sputum production or dyspnoea), but who had no diagnosis of a respiratory disease (COPD or asthma). Spirometry performed according to American Thoracic Society/European Respiratory Society criteria served as a reference test. Of the 676 subjects who entered the analyses, 398 showed normal lung function and 278 had a diagnosis of COPD (post-bronchodilator forced expiratory volume in one second/forced vital capacity of <0.70). The ability of the COPD diagnostic questionnaire to discriminate between subjects with and without COPD was poor (area under the receiver operating characteristic curve of 0.65). In a high-risk population consisting of middle-aged current smokers with a smoking history of >or=10 pack-yrs, the chronic obstructive pulmonary disease diagnostic questionnaire is probably not useful as a diagnostic tool for the identification of patients with an increased risk of airflow limitation.