The prevalence of undiagnosed chronic obstructive lung disease (COPD) is high among those who smoke heavily, according to study findings published in Respiratory Medicine.

Recent research suggests that chronic obstructive pulmonary disease (COPD) often initially goes undiagnosed, resulting in exacerbations and delayed treatment. To help determine who should undergo early spirometry testing for COPD, researchers assessed the prevalence of abnormal spirometry in a population at risk for COPD due to heavy smoking.

Using data from the Genetic Epidemiology of COPD (COPDGene; Identifier: NCT00608764) cohort, researchers retrospectively assessed spirometry patterns among individuals with a smoking history of at least 10 pack-years who did not self-report or have a physician diagnosis of COPD, asthma, emphysema, or chronic bronchitis at enrollment in COPDGene. The investigators assessed the prevalence of airflow obstruction (AFO), preserved ratio impaired spirometry (PRISm), and abnormal spirometry (AFO or PRISm) among those individuals.

Study participants were aged 45 to 80 years and self-identified as non-Hispanic White or Black/African American. All had an enrollment visit, and some had 2 follow-up visits at about 5 and 10 years post enrollment.

Spirometry was conducted based on 2005 guidelines from the American Thoracic Society/European Respiratory Society. Study participants were contacted every 6 months and completed a standardized questionnaire regarding respiratory exacerbations during the longitudinal follow-up.

The participants were categorized according to their spirometric pattern (normal, AFO, or PRISm) at enrollment. The investigators created multivariable logistic regression models to identify factors associated with abnormal spirometry.

A total of 5055 participants were included in the current analysis. Of those, 3306 (65.4%; mean [SD] age, 56.6 [8.4] years; 42.6% female) had normal spirometry, 1064 (21.0%; mean age, 61.1 [8.9] years; 38.1% female) had AFO, and 685 (13.6%; mean age, 57.1 [8.1]; 45.5% female) had PRISm.

Compared with participants with normal spirometry, participants with AFO were more likely to be older, have a greater number of pack-years of smoking, and have a history of coronary artery disease, acute bronchitis, or a chronic productive cough; those with PRISm vs normal spirometry had a higher body mass index (BMI), more pack-years of smoking, a modified Medical Research Council (mMRC) score of at least 2, and a history of coronary artery disease or hypertension.

According to multivariable analysis, having an AFO (vs normal and PRISm) spirometric pattern was associated with age, number of pack-years, current smoking, and a history of acute bronchitis. AFO occurred less frequently in individuals with greater BMI and female sex and in those who identified as Black.

In summary, we show that one-third of our participants without known obstructive lung disease despite at least 10 pack-year smoking exposure had abnormal spirometry and over two-thirds had abnormal chest imaging indicative of emphysema or small airway disease.

Among the 3467 participants who had a chest computed tomography (CT) scan at enrollment, 2865 (82.6%) had an abnormal spirometry and/or chest CT. Age and pack-years were associated with an abnormal spirometry and/or abnormal chest CT, and female sex was inversely associated.

A total of 2800 individuals completed a 5-year follow-up visit, of whom 532 (19.0%) had an incident diagnosis of COPD or were receiving new treatment for obstructive lung disease; 183 (34.4%) of those patients reported at least 1 interval exacerbation. Among the other participants, 1495 (53.4%) had normal spirometry, 490 (17.5%) had AFO, and 283 (10.1%) had PRISm.

In multivariable analysis, the composite outcome of receiving an incident COPD diagnosis or treatment with respiratory medications was associated with an mMRC score of 2 or greater, chronic productive cough, or having at least 1 exacerbation during follow-up. AFO at enrollment was associated with an incident diagnosis of COPD and/or treatment (odds ratio [OR], 1.22; 95% CI, 1.17-1.27) or PRISm (OR, 1.10; 95% CI, 1.04-1.16).

According to interval-censored proportional hazard regression models, current or former smoking status was the only variable associated with an incident diagnosis of obstructive lung disease during the follow-up. At 5 years, there was a higher percentage of individuals with COPDs among those who currently smoked vs those who previously smoked.

Among several limitations, because the COPDGene study recruited participants primarily from university medical centers, its pool of participants does not demographically reflect the general population. In addition, the analysis focused only on participants with significant smoking exposure and Black and non-Hispanic White individuals. Furthermore, the findings are based on the participants’ self-reported physician diagnosis of obstructive lung diseases and medication usage.

“In summary, we show that one-third of our participants without known obstructive lung disease despite at least 10 pack-year smoking exposure had abnormal spirometry and over two-thirds had abnormal chest imaging indicative of emphysema or small airway disease,” said study authors. They further urged clinicians to evaluate the presence of COPD in this population in order to facilitate appropriate care and prevent diagnostic delays.

Disclosure: The COPDGene study is supported in part by the COPD Foundation through contributions made to an industry advisory committee comprised of AstraZeneca, Bayer Pharmaceuticals, Boehringer-Ingelheim, Genentech, GlaxoSmithKline, Novartis, Pfizer, and Sunovion. Some of the study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.

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