An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FENO) for clinical applications

Am J Respir Crit Care Med. 2011 Sep 1;184(5):602-15. doi: 10.1164/rccm.9120-11ST.


Background: Measurement of fractional nitric oxide (NO) concentration in exhaled breath (Fe(NO)) is a quantitative, noninvasive, simple, and safe method of measuring airway inflammation that provides a complementary tool to other ways of assessing airways disease, including asthma. While Fe(NO) measurement has been standardized, there is currently no reference guideline for practicing health care providers to guide them in the appropriate use and interpretation of Fe(NO) in clinical practice.

Purpose: To develop evidence-based guidelines for the interpretation of Fe(NO) measurements that incorporate evidence that has accumulated over the past decade.

Methods: We created a multidisciplinary committee with expertise in the clinical care, clinical science, or basic science of airway disease and/or NO. The committee identified important clinical questions, synthesized the evidence, and formulated recommendations. Recommendations were developed using pragmatic systematic reviews of the literature and the GRADE approach.

Results: The evidence related to the use of Fe(NO) measurements is reviewed and clinical practice recommendations are provided.

Conclusions: In the setting of chronic inflammatory airway disease including asthma, conventional tests such as FEV(1) reversibility or provocation tests are only indirectly associated with airway inflammation. Fe(NO) offers added advantages for patient care including, but not limited to (1) detecting of eosinophilic airway inflammation, (2) determining the likelihood of corticosteroid responsiveness, (3) monitoring of airway inflammation to determine the potential need for corticosteroid, and (4) unmasking of otherwise unsuspected nonadherence to corticosteroid therapy.

Publication types

  • Practice Guideline

MeSH terms

  • Asthma / diagnosis*
  • Asthma / metabolism
  • Biomarkers / analysis
  • Breath Tests / methods*
  • Exhalation*
  • Humans
  • Lung / metabolism*
  • Nitric Oxide / analysis*


  • Biomarkers
  • Nitric Oxide