Differences in Blood Eosinophil Level During Stable Disease and During Exacerbation of COPD and Exacerbation Risks

Although blood eosinophil count (BEC) has been extensively studied as a biomarker in chronic obstructive pulmonary disease (COPD), there remain challenges and controversy in using a single reading. It has not been determined whether the difference in BEC between baseline and that during an acute exacerbation of COPD (AECOPD) has any role in predicting subsequent AECOPD.

A prospective study was conducted to investigate the possible role of differences in BEC from baseline to that during AECOPD to predict future AECOPD risk. The BEC difference was expressed as absolute eosinophil difference: BEC at index moderate-to-severe exacerbation (E_i) - baseline BEC (E₀).

Among 348 Chinese patients with COPD, 158 who experienced an index moderate-to-severe AECOPD were analyzed. Using the cut-off of 105 cells/µL for absolute eosinophil difference as determined by receiver operating characteristic (ROC) analysis, patients with absolute eosinophil difference ≥ 105 cells/µL had a shorter time to subsequent AECOPD with adjusted hazard ratio (aHR) of 1.68 (95% CI = 1.02-2.74; p = 0.040). They also had a higher annual number of subsequent AECOPD (2.49 ± 2.84/year vs 1.58 ± 2.44/year, p = 0.023). Similar findings were shown in the subgroup with stable-state baseline BEC < 300 cells/µL.

Greater difference in BEC between baseline and upon moderate-to-severe AECOPD might be associated with shorter time to next AECOPD, as well as more episodes of subsequent AECOPD.