Fractional exhaled nitric oxide (FeNO) levels and peripheral blood eosinophil counts may be useful biomarkers for clinicians in determining the presence of asthma, chronic obstructive pulmonary disease (COPD), or both in patients exhibiting clinical symptoms associated with both diagnoses, according to an article published in the Journal of Asthma.

Researchers conducted a prospective study of blood eosinophil counts and FeNO levels in patients with atopic asthma (n=30), nonatopic asthma (n=30), and COPD (n=30). In addition, serum periostin, interleukin-25 (IL-25), and immunoglobulin E (IgE) concentrations were compared in all 3 patient groups.

Results demonstrated higher blood eosinophil counts, FeNo levels, and total serum IgE concentrations (P <.001, P <.001, and P =.003, respectively) in patients with asthma compared with  patients with COPD, whereas patients with atopic-asthma were found to have increased levels of serum periostin and IgE concentrations compared with patients with nonatopic asthma and COPD (P <.05).

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In patients with asthma, FeNo levels were significantly correlated with blood eosinophil counts (r=0.430; P =.001) and serum IL-25 concentrations (r=0.338; P =.009). In addition, in patients with asthma there was a correlation between periostin concentrations and serum IgE concentrations (r=.375; P =.003) and FeNO levels (r=0.291; P <.024).

Patients with asthma were effectively distinguished from patients with COPD based on FeNO levels and peripheral blood eosinophil levels (both P <.001).

Limitations of this study include its small sample size and exclusion of nonsmoking patients.

Investigators concluded that “FeNO levels and peripheral blood eosinophil counts were useful biomarkers for distinguishing between patients with asthma and [patients with] COPD.” Therefore, clinicians should consider using these biomarkers to not only to differentiate between asthma and COPD in patients presenting with symptoms similar to both diagnoses, but also to determine the presence of asthma in patients with COPD.   

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Katoh S, Ikeda M, Shirai R, et al.  Biomarkers for differentiation of patients with asthma and chronic obstructive pulmonary disease [published online on October 16, 2017].  J Asthma. doi:10.1080/02770903.2017.1391281