Study objectives: Some patients with COPD present with significant reversibility of airflow limitation after receiving bronchodilation therapy. Leukotriene B4 (LTB4) has been implicated in the pathophysiology of both COPD and asthma. We tested the hypothesis that COPD patients with airflow reversibility and asthmatic patients who smoke might have similar levels of LTB4 in exhaled breath condensate (EBC) and sputum supernatant. The repeatability and stability of LTB4 measurements were additionally studied.
Design: Prospective, cross-sectional study.
Patients or participants: We studied 30 patients with COPD (15 smokers [FEV1, 56% predicted; SD, 6% predicted]; 15 patients with significant reversibility in airway obstruction after bronchodilation [FEV1, 14% predicted; SD, 2% predicted]). Fifteen asthmatic patients who smoked, with similar FEV1 and reversibility were also studied. Ten healthy smokers served as control subjects.
Setting: A hospital research laboratory.
Interventions: Spirometry and reversibility testing were performed on the first visit. On the following day, EBC was collected for the measurement of LTB4, and induced sputum was collected for differential cell counts and LTB4 measurement in the sputum supernatant.
Measurements and results: LTB4 levels in EBC [mean (SD)] were increased in COPD patients (mean, 86.7 pg/mL; SD, 19 pg/mL) and asthmatic patients (mean, 97.5 pg/mL; SD, 15 pg/mL) compared to control subjects (mean, 32.3 pg/mL; SD, 10 pg/mL; p < 0.0001 for both groups). COPD patients with airflow reversibility (mean, 99.8 pg/mL; SD, 12 pg/mL) had values similar to those of asthmatic patients (mean, 97.5 pg/mL; SD, 15 pg/mL; p = 0.2) and higher than those of COPD patients without airflow reversibility (mean, 73.7 pg/mL; SD, 17 pg/mL; p = 0.002). Similar results were observed in the sputum supernatant. Measurements of LTB4 in EBC and sputum were repeatable on two consecutive days, but measurements in the frozen samples of EBC and sputum were not stable after 3 weeks.
Conclusions: Patients with asthma and reversible COPD presented with higher LTB4 values compared to patients with nonreversible COPD and healthy smokers. This difference may be mainly attributed to the presence of reversibility in airway obstruction, probably as part of a common underlying inflammatory process.