IL4 and cystic fibrosis: Exhaled breath condensate (EBC) may provide a potential source of biomarkers that could be useful in a variety of diseases, including CF.118 Several potential EBC biomarkers have been investigated in CF, including EBC pH, fractional exhaled nitric oxide, leukotriene-B4, 8-isoprostane, hydrogen peroxide, interferon-γ, IL-10, IL-4, tumor necrosis factor, purines and glucose.118 At present there is insufficient evidence to support the use of any of these biomarkers as outcome measures in clinical studies.