Blood Eosinophils and Pulmonary Rehabilitation in COPD

BACKGROUND: Blood eosinophils predict the response to therapy, risk of exacerbation, and readmission in COPD. This study investigates whether blood eosinophils predict pulmonary rehabilitation (PR) outcomes in COPD. METHODS: We categorized patients into eosinophilic (blood eosinophils ≥300 cells/ml) or noneosinophilic (<300 cells/ml). In a retrospective design, we compared changes within and between the two groups on BODE index, 6-minute walk test (6MWT), FEV1, and mMRC dyspnea scale. RESULTS: Of 206 patients enrolled, 176 were included for analysis; 90 were eosinophilic. BODE index improved in both groups: (MD −1.25; 95% CI (−0.45, −4.25), P ≤ 0.001) in the eosinophilic and (MD −1.33; 95% CI (−1.72, −0.94), P ≤ 0.001) in the noneosinophilic, but a higher BODE index remained in the eosinophilic (4.98); adjusted mean change (β): 0.7 (95% CI (0.15, 1.26), P=0.01). 6MWT improved by 29.3 m in the eosinophilic (95% CI (14.2, 44.4), P ≤ 0.001) vs. 115.1 m in the noneosinophilic (95% CI (−30.4, 260.6), P=0.12). FEV1 did not change in the eosinophilic (MD −0.6; 95% CI (−2.64, 1.48), P=0.58), but improved by 2.5% in the noneosinophilic (MD 2.5; 95% CI (0.77, 4.17), P=0.005). There were no significant between-group differences in 6MWT and FEV1; adjusted mean changes (β) were −9.69 m (95% CI (−39.51, 20.14), P=0.52) and −2.31% (95% CI (−5.69, 1.08), P=0.18), respectively. There were no significant within- or between-group changes in the mMRC scale. CONCLUSION: Although PR improves the BODE index in both eosinophilic and noneosinophilic COPD, a higher eosinophil count (≥300 cells/ml) is associated with a higher (worse) BODE index. Blood eosinophils may predict PR outcomes.