The measurement of hydrogen peroxide in airways disease
Oxidative stress, caused by the production of reactive oxygen species (ROS), is a key part of the inflammatory process and has been found to be fundamental to many normal and pathological cellular activities. Hydrogen peroxide is produced during the degradation of ROS and thus can be used as a marker of inflammation. There is a great need for a noninvasive measure of airway inflammation. The collection of exhaled breath condensate is simple to perform and is relatively noninvasive. There is a variety of methods used for collection, although they are fundamentally similar. It is possible to measure hydrogen peroxide in exhaled breath condensate in patients with airway disease as well as in normal individuals. The levels of hydrogen peroxide measured are often at the lower end of the standard curve of the method used and each method has a different sensitivity, which makes direct comparison between methods difficult. Because of these methodological problems there are wide discrepancies in the concentration of hydrogen peroxide reported in breath condensate. There is a great need for standardization in the methods for collection and storage of breath condensate and in the methods used to measure hydrogen peroxide. It will then be possible to make accurate comparisons of the level of oxidative stress in many airways diseases.