Inflammatory mediators in exhaled breath, induced sputum and saliva

Summary Background and Objective Airway inflammation is assessed to monitor progression, control and treatment of asthma. The collection of exhaled breath condensate (EBC) provides a non‐invasive alternative to induced sputum samples for the monitoring of airway inflammation. Both samples can be confounded by salivary contamination. The aim of this study was to compare the levels of inflammatory mediators in samples of EBC, induced sputum and saliva samples from subjects with asthma. Method EBC, saliva and induced sputum samples were collected from subjects with asthma (n=10). Total protein, IL‐8, 8‐isoprostane and surfactant protein A (SPA) were assessed in each sample. Results Total protein, IL‐8, 8‐isoprostane and SPA were detected in all sputum samples. Only total protein and SPA were consistently measured in EBC, with levels at least 100‐fold lower than those measured in induced sputum. In saliva, total protein, SPA and 8‐isoprostane were detected in all samples, with IL‐8 detected in 60% of samples. Conclusions Induced sputum is a reliable technique that can be used to assess markers of airway inflammation. While EBC is a simple and inexpensive technique to collect lower airway secretions, the detection of inflammatory mediators is variable, and further work is required to validate this technique to assess inflammatory mediators.