Fractional exhaled nitric oxide in asthma

NICE have stated that (1):

• fractional exhaled nitric oxide (FeNO) testing is recommended as an option to help diagnose asthma in adults and children:
  • who, after initial clinical examination, are considered to have an intermediate probability of having asthma and
  • when FeNO testing is intended to be done in combination with other diagnostic options according to the British guideline on the management of asthma (2012)
  • further investigation is recommended for people whose FeNO test result is negative because a negative result does not exclude asthma
    
    
• FeNO measurement is recommended as an option to support asthma management in people who are symptomatic despite using inhaled corticosteroids.

Notes:

• nitric oxide, which is produced in the lungs and is present in exhaled breath, has been implicated in the pathophysiology of lung diseases, including asthma. It has been shown to act as a vasodilator, bronchodilator, neurotransmitter and inflammatory mediator in the lungs and airways
  
  
• FENO is a marker of asthma, and high levels correlate with ongoing eosinophilic inflammation (2)
  
  
• FENO levels typically come down with inhaled corticosteroids (ICS) in a dose-dependent manner (3)
  
  
• in case of loss of asthma control, FENO increases (4), and there are some data to suggest that serial monitoring of FENO can help in titrating corticosteroid doses (5) and predicting exacerbation (6)
  
  
• American Thoracic Society guidelines recommend the use of exhaled NO in management of asthmatics, especially in asthma with eosinophilic inflammation and in predicting response to corticosteroids

Reference:

• 1) NICE (April 2014). Measuring fractional exhaled nitric oxide concentration in asthma: NIOX MINO, NIOX VERO and NObreath
• 2) Jatakanon A et al. Correlation between exhaled nitric oxide, sputum eosinophils, and methacholine responsiveness in patients with mild asthma. Thorax. 1998;53:91-5.
• 3) Kharitonov SA et al. Dose-dependent onset and cessation of action of inhaled budesonide on exhaled nitric oxide and symptoms in mild asthma. Thorax. 2002;57:889-96.
• 4) Jones SL et al. The predictive value of exhaled nitric oxide measurements in assessing changes in asthma control. Am J Respir Crit Care Med. 2001;164:738-43.
• 5) Pijnenburg MW et al. Titrating steroids on exhaled nitric oxide in children with asthma: a randomized controlled trial. Am J Respir Crit Care Med. 2005;172:831-6.
• 6) Gelb AF et al. Role of spirometry and exhaled nitric oxide to predict exacerbations in treated asthmatics. Chest. 2006; 129:1492-9
• 7) Dweik RA et all. American Thoracic Society Committee on Interpretation of Exhaled Nitric Oxide Levels (FENO) for Clinical Applications. 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.