Nasal and Pharyngeal Eosinophil Peroxidase Levels Represent Surrogate Biomarkers for the Presence of Lower Airway Eosinophils in Adults with Poorly Controlled Asthma
Sunday, March 6, 2016
South Exhibit Hall H (Convention Center)
Matthew A Rank, MD, Sergei I. Ochkur, PhD, John C Lewis, MD, Harry G. Teaford, MD, Lewis J Wesselius, MD, Richard A Helmers, MD, Nancy A Lee, PhD, Parameswaran K. Nair, MD PhD FRCP FRCPC, James J. Lee, PhD
Rationale: Systematic review and meta-analyses of available studies suggest that titrating inhaled corticosteroids using sputum eosinophil percentage is an effective strategy to reduce the frequency of asthma exacerbations. This study performs a direct comparison of nasal, pharyngeal, and sputum eosinophil peroxidase (EPX) levels with induced sputum eosinophil percentage in adults with poorly controlled asthma and normal controls.

Methods: Adults with asthma and normal controls were prospectively enrolled. A nasal swab, pharynx swab, spontaneous sputum, and induced sputum were recovered. EPX was measured using an ELISA and normalized in nasal and pharynx specimens for total protein content and in sputum for mL-gram of protein. EPX levels between asthma and control subjects were compared using the Wilcoxon signed-rank test; Spearman’s coefficient was used to assess correlation between EPX levels and sputum eosinophil percentages.

Results: Ten asthma and 10 control subjects were enrolled. Sputum EPX, measured by our novel ELISA, were statistically different between asthma and control subjects (p=0.024). EPX levels measured in the nasal and pharyngeal swab samples derived from the same patients were also different between asthma and control subjects, each displaying a high degree of significance (p=0.002). Spearman’s correlation coefficients for nasal EPX and pharyngeal EPX levels compared to induced sputum eosinophil percentage were 0.81 (p=0.0007) and 0.78 (p=0.0017), respectively.

Conclusions: There is a strong association in a given patient between both nasal and pharyngeal EPX levels and induced sputum eosinophil percentage. Thus, the use of these minimally-invasive diagnostic clinical metrics may provide novel point-of-care assays in the management of asthma patients.