Fractional exhaled nitric acid has been found to be low in airway inflammation. Its use has been sporadic in appropriate clinical settings, to diagnose and determine the response to steroids. Here is a guideline to its interpretation.

    Team@CMHF

The American Thoracic Society has issued the first-ever guidelines on the use of fractional exhaled nitric oxide (FENO) that address when to use FENO and how to interpret FENO levels in different clinical settings.

While the measurement is standardized, the interpretation is not. This document gives a framework for the interpretation of FENO in the appropriate clinical setting.”

While the recommendations set forth in the guidelines are unlikely to contain any surprises to those already using FENO in clinical practice, they emphasize the importance of the clinical context for the correct interpretation of FENO and highlight the utility of clinically significant cut points instead of normal values.

The guidelines also separate the use of FENO for diagnosis from the use for monitoring patients with known asthma.

The guidelines recommend that FENO be used to:

• Diagnose eosinophilic airway inflammation;
• Determine the likelihood of corticosteroid responsiveness in individuals with chronic respiratory symptoms  possibly due to airway inflammation;
• Support the diagnosis of asthma in situations where objective evidence is needed; and
• Monitor airway inflammation in patients with asthma.

Finally, guidelines suggest that clinicians consider FENO increases of 20 percent or more for values over 50 ppb (or 10 ppb more for values less than 50ppb) a significant increase from one visit to the next, and, conversely, reductions of 20 percent or 10ppb indicate significant response to anti-inflammatory therapy.

Rapid technological advances are one reason that more research is needed. “We need to have more appropriately designed clinical trials evaluate the use for FENO in different clinical settings and to include FENO as an end point in clinical trials,” he concluded.

Ref: http://www.eurekalert.org/pub_releases/2011-09/ats-apc083111.php