ABSTRACT
Many lung diseases, including asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, cystic fibrosis, and interstitial lung disease, involve chronic inflammation and oxidative stress. Yet these are not measured directly in routine clinical practice because of the difficulties of monitoring inflammation. In asthma, fiber-optic bronchial biopsies have become the “gold standard” for measuring inflammation in the airway wall, but this is an invasive procedure that is not suitable for routine clinical practice and cannot be repeated often. It is also unsuitable for use in children and patients with severe disease. Symptoms may not accurately reflect the extent of underlying inflammation, due to differences in perception and masking by bronchodilators in airway disease. Measurement of airway hyperresponsiveness by histamine or methacholine challenge has been used in asthma as a surrogate marker of inflammation, but interpretation is confounded by the use of bronchodilator therapy. Furthermore, it is difficult to perform this measurement in children and in patients with severe disease. This has led to the use of induced sputum to detect inflammation.
