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JACI Highlights - October 2009How to interpret FENO measurements?There is uncertainty about how exhaled nitric oxide measurements should be interpreted in individual patients with asthma. In general, high levels (implying uncontrolled airway inflammation) and low levels (implying well-controlled inflammation) are helpful in assessing disease activity and its relationship to symptoms. Intermediate levels are indeterminate. Yet what is high and what is low? Cutpoints of >50 ppb and <25 ppb in adults are recommended, but are these always appropriate? In the study by Smith et al. in the October 2009 issue of The Journal of Allergy and Clinical Immunology, FENO levels were measured (a) when asthma was poorly controlled, (b) after a course of oral prednisone when asthma was well controlled (personal best), and (c) during optimum treatment with inhaled steroid. All of the results were compared against predicted values for healthy subjects derived from recently published reference equations. It was found that targeting asthma treatment to achieve either predicted values or personal best values is not necessary. Adequate asthma control can be achieved with inhaled steroids at somewhat higher than “personal best” FENO levels. The authors conclude that measuring FENO during periods of good asthma control establishes the best “baseline” in individual patients and that subsequent changes should be used to guide clinical assessment. “Exhaled nitric oxide levels in asthma: "personal best" versus reference values” by Smith et al. (JACI October 2009 Volume 124 No. 4) |
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