Non-invasive biomarkers in exacerbations of obstructive lung disease

Current methods of diagnosing exacerbations of asthma and chronic obstructive pulmonary disease (COPD) shed little light on their aetiology or pathophysiology. This study aimed to define the inflammatory biomarker profile of subjects with obstructive lung disease and to compare these with control subjects also with respiratory infections, using exhaled breath condensate (EBC) and induced sputum biomarker analysis.

EBC, induced sputum and C-reactive protein were collected from subjects with exacerbations of asthma (n = 28), exacerbations of COPD (n = 29) and otherwise healthy controls with symptoms of respiratory tract infection (n = 28). Subjects were tested again after recovery. EBC and induced sputum were analysed for protein, hydrogen peroxide, interferon gamma inducible protein-10 (IP-10), neopterin, interleukin (IL)-6, IL-8, leukotriene B4 and tumour necrosis factor (TNF)-α. Sputum cell counts and EBC pH were also analysed.

EBC pH was significantly lower in exacerbation compared with recovery (5.54 0.07 vs 6.04 ± 0.08; P < 0.001). The novel markers IP-10 and neopterin were significantly increased in induced sputum supernatant (pooled groups pre and post exacerbation: IP-10: 188.6 ± 102.1 vs 5.40 ± 1.28 pg/mL, P = 0.006; neopterin: 15.81 ± 2.50 vs 5.38 ± 0.45 nmol/L, P < 0.0001), as was TNF-α (137.8 ± 49.64 vs 71.56 ± 45.03 pg/mL, P = 0.018). Few other biomarkers proved significantly different in exacerbation, although C-reactive protein was raised.

Non-invasive biomarker assessment may provide useful information in exacerbation of obstructive lung diseases, particularly sputum IP-10 and neopterin and EBC pH.