Predictive value of blood eosinophil count in COPD

Abstract

See related https://onlinelibrary.wiley.com/doi/10.1111/resp.14024

Reply

“…We read with great interest the recent study by Ko et al, 1 investigating the impact of blood eosinophilia in patients with chronic obstructive pulmonary disease (COPD). They identified a cut-off value of 144/μL for eosinophil count and found that high eosinophil count (>144/μL) was associated with shorter hospital length of stay.…”

“…However, the definition of cut-off values appears inconsistent as median value (100/μL), predefined values (150 and 300/μL) and Youden index from receiver operating characteristic curve (144/μL) have been proposed. 1 This discrepancy reduces the external applicability of eosinophil count as a predictive marker.…”

“…First, consistent with most previous studies, eosinophil count was included in the generalized linear models as a continuous variable in the current study, based on a linear assumption between eosinophil and the dependent outcomes. 1 However, for a biomarker with a normal range, the relationship with clinical outcomes may be non-linear. The platelet/lymphocyte ratio (PLR) is a good example.…”

“…Second, the impact of missing confounders should also be evaluated. The current linear model used by Ko et al 1 did not adjust for inhaled and systemic corticosteroid use despite a potential interaction or mediation effect between eosinophil count and the use of inhaled corticosteroids (ICS). For instance, according to the pooled result from the European Respiratory Society Guideline, 3 the detrimental effect of ICS withdrawal was only significant in patients with eosinophil counts >300/ μL, while in patients with eosinophil counts <300/μL, ICS withdrawal did not increase the exacerbation risk.…”

“…We thank Zhu et al 1 for their interest in our previous study on 'Blood eosinophil count as a predictor of hospital length of stay in COPD exacerbations'. 2 We agree that there is increasing evidence that type-2 airway inflammation plays an important role in chronic obstructive pulmonary disease (COPD).…”