Clinical science
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It has been reported that small airway inflammation is closely associated with the severity of airflow limitation in COPD (chronic obstructive pulmonary disease). We tested a new method of measurement of biochemical constituents in ELF (epithelial lining fluid) obtained separately from the central or peripheral airways using a bronchoscopic microsampling technique. The present study was designed to determine the validity of measuring CML [N(epsilon)-(carboxymethyl)lysine] levels in ELF for the assessment of small airway inflammation in COPD. ⋯ In COPD patients, the CML level in peripheral airways was significantly correlated with FEV1 (forced expiratory volume in 1 s) (r=-0.82, P=0.002) and FEV1/FVC (forced vital capacity) (r=-0.57, P=0.03). Moreover, CML levels in peripheral airways were significantly correlated with levels of both 8-isoprostane (r=0.76, P=0.003) and IL-8 (r=0.67, P=0.01). In conclusion, these findings suggest that elevated levels of CML in ELF from peripheral airways were observed in COPD patients, and this parameter was correlated with the severity of airflow limitation.