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Heterogeneous burden of lung disease in smokers with borderline airflow obstruction

Pirozzi, Cheryl S.; Gu, Tian; Quibrera, Pedro M.; Carretta, Elizabeth E.; Han, MeiLan K.; Murray, Susan; Cooper, Christopher B.; Tashkin, Donald P.; Kleerup, Eric C.; Barjaktarevic, Igor; Hoffman, Eric A.; Martinez, Carlos H.; Christenson, Stephanie A.; Hansel, Nadia N.; Graham Barr, R.; Bleecker, Eugene R.; Ortega, Victor E.; Martinez, Fernando J.; Kanner, Richard E.; Paine, Robert

Background
The identification of smoking-related lung disease in current and former smokers with normal FEV1 is complex, leading to debate regarding using a ratio of forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC) of less than 0.70 versus the predicted lower limit of normal (LLN) for diagnosis of airflow obstruction. We hypothesized that the discordant group of ever-smokers with FEV1/FVC between the LLN and 0.70 is heterogeneous, and aimed to characterize the burden of smoking-related lung disease in this group.

Methods
We compared spirometry, chest CT characteristics, and symptoms between 161 ever-smokers in the discordant group and 940 ever-smokers and 190 never-smokers with normal FEV1 and FEV1/FVC > 0.70 in the SPIROMICS cohort. We also estimated sensitivity and specificity for diagnosing objective radiographic evidence of chronic obstructive pulmonary disease (COPD) using different FEV1/FVC criteria thresholds.

Results
The discordant group had more CT defined emphysema and non-emphysematous gas trapping, lower post-bronchodilator FEV1 and FEF25–75, and higher respiratory medication use compared with the other two groups. Within the discordant group, 44% had radiographic CT evidence of either emphysema or non-emphysematous gas trapping; an FEV1/FVC threshold of 0.70 has greater sensitivity but lower specificity compared with LLN for identifying individuals with CT abnormality.

Conclusions
Ever-smokers with normal FEV1 and FEV1/FVC <  0.70 but > LLN are a heterogeneous group that includes significant numbers of individuals with and without radiographic evidence of smoking-related lung disease. These findings emphasize the limitations of diagnosing COPD based on spirometric criteria alone.

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Also Published In

Title
Respiratory Research
DOI
https://doi.org/10.1186/s12931-018-0911-z

More About This Work

Academic Units
Medicine
Published Here
March 27, 2019

Notes

Chronic obstructive pulmonary disease, Pulmonary function tests, Spirometry, Airway obstruction, Emphysema, Forced expiratory volume, Maximal Midexpiratory flow rate