How are fractional exhaled nitric oxide (FENO) measurements interpreted?

Updated: May 14, 2020
  • Author: Kevin McCarthy, RPFT; Chief Editor: Nader Kamangar, MD, FACP, FCCP, FCCM  more...
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Answer

Answer

Table 6. Use of FENO in Evaluation of Cough and/or Wheeze and/or Dyspnea [23] (Open Table in a new window)

 

FENO <25 ppb

(<20 ppb in children)

FENO 25-50 ppb

(20-35 in children)

FENO >50 ppb

(>35 ppb in children)

Symptoms present in the past 6 weeks or longer

- Eosinophilic airway inflammation unlikely

- Consider alternative diagnoses

- Unlikely to benefit from ICS

- Interpret with caution

- Consider clinical context

- Monitor change in FENO over time

- Consider variables like atopy and smoking

- Eosinophilic airway inflammation present

- Likely to benefit from ICS

Table 7. Use of FENO for Monitoring (in Patients with Diagnosed Asthma) [23] (Open Table in a new window)

 

FENO <25 ppb

(<20 ppb in children)

FENO 25-50 ppb

(20-35 in children)

FENO >50 ppb

(>35 ppb in children)

Symptoms present

- Consider alternative diagnoses

- Unlikely to benefit from increase in ICS

- Persistent allergen exposure

- Inadequate ICS dose

- Poor compliance

- Steroid resistance

- Persistent allergen exposure

- Poor compliance or inhaler technique

- Inadequate ICS dose

- Risk for exacerbation

- Steroid resistance

Symptoms absent

- Adequate ICS dose

- Good compliance

- Consider ICS taper

- Adequate ICS dosing

- Good compliance

- Monitor change in FENO

- ICS withdrawal or dose reduction may result in relapse

- Poor compliance or inhaler technique