Blood Eosinophils Threshold Could Predict ICS Treatment Response for COPD

There is an increased need for potential biomarkers that can identify patients with chronic obstructive pulmonary disease (COPD) who will benefit from treatment involving inhaled corticosteroids (ICS). According to a recent study, the 2% threshold for blood eosinophils could accurately predict ICS treatment response in patients with COPD, but the risk of pneumonia was increased.

The researchers conducted an electronic search in the PubMed and EMBASE databases in order to find relevant studies published up to 2017. Data was extracted from relevant studies that included the keywords COPD, eosinophil, and clinical trial. Also, primary research articles were compared for studies of ICS treatment and annual rates of moderate/severe exacerbations in those with COPD with <2% and ≥2% blood eosinophils.

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“Inhaled corticosteroids (ICSs) can reduce acute exacerbation in patients with COPD having moderate-to-very severe lung function defects and a history of frequent exacerbation. However, the risks and benefits of ICS treatment are still controversial, especially the purported increase in pneumonia incidence,” the authors explained. “Airway eosinophilia is a hallmark inflammatory response for asthma pathogenesis and is now known to be involved in the airway inflammatory process in COPD.”

Five studies were included in the study, totaling with 12,496 patients with moderate-to-very severe COPD. At baseline, 60% of patients had ≥2% blood eosinophils; however, the analysis demonstrated a 17% reduction in exacerbation of moderate/severe COPD in patients with ≥2% blood eosinophils undergoing ICS therapy, compared to the non-ICS/ICS withdrawal/placebo group.

The researchers also found that the risk of pneumonia-related events was significantly increased in the subgroup with eosinophil count ≥2% undergoing ICS-containing treatments. Additionally, there was no significant difference in the subgroup with eosinophil count <2%.

“During a COPD exacerbation, both absolute and relative eosinophil counts in sputum are significantly increased compared with those during the stable phase,” the authors stated. “Therefore, eosinophils may contribute to increased airway inflammation during acute exacerbations of COPD. Additionally, blood eosinophilia is associated with a higher risk of COPD exacerbation, which may lead to a decline in lung function and increased mortality.”

Although the results suggest a modest benefit from ICS-containing treatments compared with non-ICS/ICS withdrawal/placebo treatments, further studies are needed with prespecified criteria for blood eosinophil subgroups in order to identify the best cutoff point for blood eosinophil count, the researchers concluded. They also noted the need for a comprehensive assessment of the relationship between eosinophil counts and the treatment effects of ICS regimens.

Reference

Cheng, SL. Blood eosinophils and inhaled corticosteroids in patients with COPD: systematic review and meta-analysis. [published online September 6, 2018]. Int J Chron Obstruct Pulmon Dis. doi: 10.2147/COPD.S175017.