In response to the Agency for Healthcare Research and Quality statement questioning the usefulness of “screening spirometry,” the National Heart, Lung, and Blood Institute and the COPD Foundation held a consensus conference in June 2008 to establish a procedure to detect cases of COPD in the general population. Conference participants developed a three-stage approach, using a brief questionnaire, peak flow measurement with a pocket spirometer, and diagnostic quality spirometry. The overall objective of this study was to examine the usefulness of a simple questionnaire and peak flow measurement in screening for COPD in a self-selected population. We hypothesized that this combination would efficiently screen for clinically relevant COPD.
We queried individuals attending public events regarding the presence of wheeze and/or asthma, mucus production, dyspnea, exposure to irritants, and tobacco use. Peak expiratory flow (PEF) was then measured with a pocket spirometer. If PEF was < 70% predicted, spirometry was performed. In order to estimate the false-negative rate, a random sample of every 10th participant was also selected for spirometry.
Between June 2008 and December 2009, 5,761 adults completed the risk assessment questionnaire. The mean age of the respondents was 54 years, 58% were women, and 88% were white. Of these, 5,638 participants completed pocket spirometry, and 315 (5.6%) had PEF < 70% predicted. Of 5,323 with normal PEF, 651 underwent spirometry. The performance of PEF was assessed via positive and negative predictive values relative to a diagnosis of clinically significant airflow obstruction, defined as FEV1/FEV6 < the lower limit of normal and FEV1 < 60% predicted. Of 4,238 subjects with at least two risk factors, 267 (6.3%) had PEF < 70%, compared with 48 of the 1,400 subjects (3.4%) with fewer than two risk factors (P < .001). Based on 729 participants with acceptable spirometry, 63.1% (113 of 179) of those with abnormal PEF tested positive for clinically significant airflow obstruction, compared with 5.5% (30 of 550) with normal PEF (P < .001). The estimated prevalence of significant COPD among the 5,638 screened was 8.7%, and sensitivity and specificity were 40.7% and 97.7%, respectively.
A staged approach to COPD screening in adults is useful for detecting clinically significant airflow obstruction in our study population.