Comparative study of periostin expression in different respiratory samples in patients with asthma and chronic obstructive pulmonary disease

INTRODUCTION    Periostin is considered to be a marker of eosinophilic inflammation in patients with asthma. However, there are no literature data on periostin in patients with chronic obstructive pulmonary disease (COPD).
OBJECTIVES    The aim of the study was to evaluate periostin expression and to compare its concentrations in various materials in patients with mild-to-moderate asthma and COPD, as well as to evaluate the potential association between periostin and clinical features of both diseases.
PATIENTS AND METHODS    Using an enzyme-linked immunosorbent assay, we measured periostin concentrations in serum, induced sputum (IS), exhaled breath condensate (EBC), and bronchoalveolar lavage fluid (BALF) as well as periostin expression in bronchial biopsy samples in 24 patients with asthma, 36 patients with COPD, and 12 controls. Correlations between periostin levels in different materials were also analyzed and periostin concentrations were compared between patients with asthma and those with COPD.
RESULTS    Periostin levels were detectable in serum, IS, EBC, and BALF from patients with asthma, COPD, and controls. EBC periostin levels correlated with tissue periostin expression and were significantly higher in asthma than in COPD (P = 0.04). Periostin expression in bronchial mucosa was higher in asthma than in COPD (P <0.001), as well as in asthma and COPD patients compared with controls (P <0.001). No significant correlations between tissue periostin expression and BALF, IS, or serum periostin levels were found. There were no differences in serum, IS, BALF, or EBC periostin concentrations between patients with different phenotypes of both diseases.
CONCLUSIONS    Periostin may be detected not only in serum, IS, and airway tissue samples, but also in EBC and BALF. EBC periostin levels and tissue periostin expression are higher in patients with asthma than in those with COPD. EBC periostin levels may serve as a potential surrogate marker for tissue periostin expression.