Purpose of Technology: The measurement of nitric oxide (NO) concentration in expired breath has been introduced as an adjunct to or replacement for the established clinical and laboratory assessments for the diagnosis of asthma. Measurement of fractional exhaled nitric oxide (FENO) is a noninvasive diagnostic technique. The NO molecules exhaled in breath can be measured using a handheld electrochemical sensor or a large, stationary chemiluminescence gas analyzer.

Controversy: NO, which is normally produced by the respiratory tract mucosa, is believed to be a powerful mediator involved in airway inflammation. The level of FENO should serve as a surrogate indicator or marker of airway inflammation, which can aggravate or be the primary cause of asthma. Asthma is a complex disease that has many potential contributing factors. Measurement of FENO may not be highly accurate for asthma diagnosis since it detects only 1 of these factors or FENO may only be accurate for diagnosis of a certain specific type of asthma such as eosinophilic or allergic asthma.

Relevant Questions:

  • How accurate is exhaled NO breath testing for the diagnosis of asthma?

  • Is FENO measurement safe?

  • Which patients might be suitable candidates for diagnosis of asthma based on FENO?

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