An eye to the future: exhaled nitric oxide as a predictor of clinical outcomes in asthma

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Recent guidelines for the management of asthma now emphasise the importance of anticipating what lies ahead. The concept of “future risk” has been introduced into our clinical terminology 1. While it may be argued that clinicians have always intuitively paid attention to ideas of future risk as well as future benefit, it is only recently that these have been articulated. Future risk refers to the risk of adverse outcomes such as exacerbations, poor asthma control, accelerated decline in lung function or side-effects of treatment in the near or distant future 2. Similarly, although anticipating future benefit may seem easy, it is not: the response to most asthma treatments is heterogeneous, and predicting those who are likely to benefit from a therapeutic intervention is possible in only a proportion of patients. This is particularly true for anti-inflammatory treatment 3, 4, and many clinicians prescribe empirically. In asthma studies, the effect of an intervention on some future risks ( e.g. exacerbations) may be measured directly, or inferences may be drawn from measuring physiological variables or biomarkers. The latter are of increasing importance because the future benefits and risks associated with treatment intervention may be related to control of the underlying disease process, as reflected in biomarker levels. For asthma exacerbations, we can assess future risk in three ways. Firstly, we can identify epidemiological factors that characterise the “at risk” patient, e.g. male sex, ethnicity, smoking history 5. Second, there is the patient's individual history. The past is a good predictor of the future. …