A bronchodilator response (BDR) grading system that uses either volume percentage change in forced expiratory volume in 1 second (FEV1) or forced vital capacity (FVC) can identify differences in exercise performance, exacerbation frequency, and dyspnea in people who smoke or who have a prior smoking history, according to study results published in the Annals of the American Thoracic Society.
Participants from the COPDGene cohort, a population of current or ex-smokers with or without COPD defined by spirometry, were included in the analysis (n=10,311). Researchers identified participants’ largest FEV1 and FVC with 3 prebronchodilator and 3 postbronchodilator maneuvers. Several bronchodilator categories of FEV1 response by volume or percentage FEV1 change were formed based on the 7741 participants who had a coefficient of variation for FEV1 and FVC was <15%. These categories included negative (≤0.00% or ≤0.00 L), minimal (>0.00% to ≤9.00% or >0.00 L to ≤0.09 L), mild (>9.00% to ≤16.00% or >0.09 L to ≤0.16 L), moderate (>16.00% to ≤26.00% or >0.16 L to ≤0.26 L), and marked (>26.00% or >0.26 L).
Approximately 12% and 33% of participants met mild and moderate or marked BDR-FVC criteria, respectively. Another 20% and 31% met moderate or marked BDR-FEV1 criteria, respectively. Only 20.6% of participants met the American Thoracic Society/European Respiratory Society positive criteria.
Compared with the negative BDR-FEV1 category, a greater 6-minute walking distance was associated with the minimal (mean difference [MD], 8.46; 95% CI, 2.01-14.91), mild (MD, 17.60; 95% CI, 10.61-24.58), moderate (MD, 26.94; 95% CI, 19.81-34.07), and marked (MD, 37.00; 95% CI, 29.14-44.86) BDR-FEV1 categories.
Lower St. George’s Respiratory Questionnaire scores were also associated with the minimal (% difference, -7.30; 95% CI, -13.00 to -1.20), mild (% difference, -8.30; 95% CI, -14.40 to -1.80), moderate (% difference, -12.20; 95% CI, -18.20 to -5.80), and marked (% difference, -12.40; 95% CI, -18.90 to -5.30) BDR-FEV1 categories compared with the negative category. Similarly, lower modified Medical Research Council dyspnea scores were associated with the minimal (odds ratio [OR], 0.81; 95% CI, 0.71-0.93), mild (OR, 0.74; 95% CI, 0.64-0.86), moderate (OR, 0.62; 95% CI, 0.53-0.73), and marked (OR, 0.63; 95% CI, 0.53-0.75) BDR-FEV1 categories.
Fewer exacerbations were associated with the moderate (relative risk, 0.86; 95% CI, 0.74-0.99) and marked (relative risk, 0.74; 95% CI, 0.63-0.87) BDR-FEV1 categories compared with negative BDR. Additionally, lower computerized tomography airway wall thickness was associated with minimal BDR (MD, -0.24; 95% CI, -0.43 to -0.06) relative to the negative BDR-FEV1 category.
A limitation of the study was the lack of healthy never-smokers, which may limit the generalizability of the findings.
The researchers concluded that “whether these BDR categories have prognostic implications remains to be tested.”
Hansen JE, Gorek Dilektasli A, Porszasz J, et al; for the COPDGene Investigators. A new bronchodilator response grading strategy identifies distinct patient populations [published online August 12, 2019]. Ann Am Thorac Soc. doi:10.1513/AnnalsATS.201901-030OC