The exhaled biomarker puzzle: bacteria play their card in the exhaled nitric oxide–exhaled breath condensate nitrite game

The measurement of exhaled biomarkers has gained increasing interest in recent years, mainly driven by the unmet clinical need to monitor airway inflammation and the response to anti-inflammatory treatment. The current issue of Thorax contains two important publications in this rapidly growing field. The study by Pijnenburg et al shows how exhaled nitric oxide (NO) measurement can serve clinical practice,¹ while the investigation by Marteus et al draws attention to the potential pitfalls of measuring nitrite in exhaled breath condensate (EBC).²

It was hardly more than a decade between the discovery by Gustaffson et al in 1991 that the exhaled breath contains NO and the approval of such a measurement for clinical practice to monitor the effect of anti-inflammatory treatment in asthma.^3,4 The road has been paved by approximately 2000 publications on the measurement of the fractional concentration of exhaled nitric oxide (FE_NO) in health and disease, including three guidelines which provide methodological recommendations by internationally known experts in the field and endorsed by the European Respiratory Society (ERS) and/or the American Thoracic Society (ATS).^5–7 By using these recommendations, exhaled NO can be …