FeNO: An Adjunct for Asthma Management in Primary Care?

Nitric oxide (NO) is produced by airway epithelial cells and its production is increased in inflammatory conditions. Clinically, NO can be measured in exhaled breaths. Since NO is increased with inflammation, the fraction of exhaled NO (FeNO) is a surrogate for eosinophilic airway inflammation and has been used as noninvasive marker of asthma activity and eosinophilic lung disease.

Measurement of FeNO may be a practical tool for primary care physicians who manage patients with asthma. The utility and desirability of the test were explored at the 2015 American College of Chest Physicians (CHEST 2015) meeting in Montreal, where Dr. Mark Turner, from the University of British Columbia in Vancouver, discussed the findings of his new research, “Utility of FeNO measurements for family physicians in managing uncontrolled asthma.”

American Thoracic Society clinical practice guidelines, recommend the use of FeNO in the diagnosis of eosinophilic lung disease and in asthma when objective information can determine the likelihood of steroid responsiveness. A FeNO level >45 ppm is considered to be a marker for steroid responsiveness; a level of <25 ppm (<20 ppm in children), the absence of eosinophilic disease and a response to steroids with asthma is unlikely. Serial FeNO levels can also be used as markers of response to therapy and a decrease of 20% or 10 ppm (if the value is less than 50 ppm) indicates a significant response to anti-inflammatory treatment.

The main advantages of this test are its non-invasiveness, repeatability, ease of use, and rapid results. The downsides are availability, cost, and lack of sensitivity and specificity.

For their research, Dr Turner and his study team provided family physicians caring for 32 adult patients with mild uncontrolled asthma with FeNO results and an algorithm for result interpretation. A cut-off of 30 ppm was used to define a level representative of active inflammation. The mean FEV₁ of the patients was 82% of predicted and a mean asthma control questionnaire score was 1.6 (the score is a measure of asthma control where 0 = no impairment, 6 = maximum impairment). Of the patients tested, 46% had an abnormal FeNO level (>30 ppm). Family physicians found the information obtained from the FeNO results helpful. Based on a questionnaire filled out by these clinicians, >40% of them thought FeNO levels were helpful in managing asthma and 75% said they would use FeNO as part of their management algorithm. Their use of FeNO led to a change in inhaled steroid dose in 50% of the patients. There was no correlation between FeNO levels and the asthma control questionnaire completed by the enrolled patients.

The researchers concluded that when FeNO results are available to family physicians of asthma patients, it is a useful adjunct in management and clinicians found it helpful. The senior author practices primary care and loves additional objective markers that measure asthma control. He is looking forward to more access to FeNO levels.

References:

Turner M. Asthma outcomes: utility of FeNO measurements for family physicians managing mildly uncontrolled asthma patients. Presentation at 2015 American College of Chest Physicians meeting (CHEST 2015); October 25, 2015; Montreal, Canada.

Dweik RA, Boggs PB, Erzurum SC, et al. An official ATS clinical practice guideline: interpretation of exhaled nitric oxide levels (FENO) for clinical applications. Am J Respir Crit Care Med. 2011;184:602-15. doi: 10.1164/rccm.9120-11ST. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4408724/

Barnes PJ, Dweik RA, Gelb AF, et al. Exhaled nitric oxide in pulmonary diseases: a comprehensive review. Chest. 2010;138:682-692. doi: 10.1378/chest.09-2090. Review. http://www.ncbi.nlm.nih.gov/pubmed/?term=10.1378%2Fchest.09-2090.

Lougheed MD, Canadian Thoracic Society Asthma Clinical Assembly. Canadian Thoracic Society 2012 guideline update: Diagnosis and management of asthma in preschoolers, children and adults: executive summary. Can Respir J. 2012;19(6):e81-8.  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4527232