Chronic obstructive pulmonary disease (COPD), estimated to be the third leading cause of death worldwide, is a significant cause of morbidity and mortality. Epidemiologic studies often use items related to physician-diagnosed COPD. A lack of validation and standardization of these items exists.
Thus, researchers of an analysis published in the International Journal of Chronic Pulmonary Disease conducted a validation study in the general population in which access to spirometry was available both before and after bronchodilation.
A total of 1050 participants aged 50 to 64 years completed a questionnaire and underwent spirometry, which included forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) after inhalation of salbutamol 400 μg. COPD was defined as an FEV1/FVC ratio <0.7 after bronchodilation. All study data were derived from the pilot portion of the Swedish Cardiopulmonary Bioimage Study (SCAPIS).
Physician-diagnosed COPD was defined as an affirmative response to the following question: “Have you ever had COPD diagnosed by a physician?” Other questions in the survey involved the combined items of COPD or emphysema; the presence of chronic bronchitis; the combined items of COPD, emphysema, or chronic bronchitis; and the presence of asthma.
The sensitivity was 0.057 and specificity was 0.989 for the question about physician-diagnosed COPD, relative to both physician-diagnosed COPD and spirometry-defined COPD. The sensitivity of the combined items involving COPD or emphysema in detecting COPD was also 0.057, and the specificity was 0.985. Regarding physician-diagnosed chronic bronchitis, the sensitivity was 0.090 and the specificity was 0.968. When the items related to physician-diagnosed COPD, emphysema, or chronic bronchitis were combined as 1 entity, the sensitivity rose to 0.113 and the specificity declined to 0.957.
The investigators concluded that questions involving physician-diagnosed COPD have low sensitivity and high specificity, reducing the number of false-positive results. This low sensitivity can lead to underestimating the total burden of COPD in the general population. Items concerning physician-diagnosed COPD may be useful in future studies of risk factors for COPD, but are not recommended in prevalence studies.
Torén K, Murgia N, Olin AC, et al. Validity of physician-diagnosed COPD in relation to spirometric definitions of COPD in a general population aged 50-64 years – the SCAPIS pilot study. Int J Chron Obstruct Pulmon Dis. 2017;12:2269-2275.