Post-bronchodilator Reversibility of FEV₁ and Eosinophilic Airway Inflammation in COPD

The relationship between bronchodilator responsiveness and eosinophilic airway inflammation has not been well documented in COPD. It has been investigated in this retrospective study. This issue has grown in importance due to increasing interest in the asthma-COPD overlap syndrome.

264 stable COPD patients with no past history of asthma were retrospectively analyzed. Correlation analyses between FEV₁ reversibility and sputum eosinophil levels were conducted. Sputum eosinophil levels were dichotomized using FEV₁ reversibility cut-off points (>0.4L and >15% vs. >0.2L and >12%) and compared. The effectiveness of FEV₁ reversibility to predict sputum eosinophilia (>3%) was analyzed with a logistic regression and a ROC analysis.

82 (31.1%) patients with higher FEV₁ reversibility values (0.14 vs. 0.11L, P=.01) presented sputum eosinophilia. FEV₁ reversibility was weakly correlated with the sputum eosinophil level (r=0.162, P=.008). Patients with FEV₁>0.4L and >15% increment had higher sputum eosinophil levels (6.11 vs. 1.02%, P=.049) whereas the level did not differ when dichotomized by FEV₁ increment >0.2L and >12%. Very positive FEV₁ reversibility (>0.4L and >15%) predicted sputum eosinophilia after adjustment forage, baseline FEV₁ and FVC (OR: 4.262, P=.029). In the ROC analysis, the AUC was 0.58 (P=.034), and FEV₁ increment>0.4L and >15% had a positive predictive value of 63.6% and an overall accuracy of 70.1%.

FEV₁ reversibility was weakly correlated with sputum eosinophil levels in COPD. Positive FEV₁ reversibility (>0.4L and >15%) is moderately successful in predicting sputum eosinophilia (>3%).