FeNO
The fractional exhaled nitric oxide (FeNO) test measures the level of NO in the exhaled breath and provides an indication of eosinophilic inflammation in the lungs.
A PCRS Consensus: FeNO testing for asthma diagnosis
The fractional exhaled nitric oxide (FeNO) test measures the level of NO in the exhaled breath and provides an indication of eosinophilic inflammation in the lungs.
Guide to FeNO Testing
In this article produced for Practice Nurse, author, PCRS Chair, Carol Stonham, describes FeNO testing and its role in diagnosing respiratory disease. She discusses the advantages and limitations of this test.
FeNO for the diagnosis and management of asthma
Resources from the Academic Health Science Network (AHSN) Programme
Primary Care Respiratory Society (PCRS) position statement
A personal perspective on using the plan on a page tool to support the development of FeNO services. An article on using the FeNO Plan-on-a-Page tool, with accompanying working example and editable template.
The PCRS Integrated Care Board (ICB), Health Board and Trust toolkit aims to support healthcare commissioners across the UK to implement the new BTS/NICE/SIGN asthma guideline effectively and ensure the best possible care and outcome for all their asthma patients.
PCRS welcomes the opportunity that digital respiratory healthcare and the collection and analysis of respiratory data could bring. However, new technology for use in primary care must be interoperable with current patient consultation and management systems, should not be mandated for patients and should be an option as part of shared decision making. New respiratory digital health interventions must, as well as being clinically and cost effective also preferentially attend to the factors that currently maintain respiratory health inequality.
Spirometry is a component of the diagnosis and management of respiratory conditions in primary care and should ideally be performed via referral to a primary care network respiratory diagnostic service or community diagnostics centre (CDC) with expertise in the diagnosis of the most common respiratory conditions and of less common diagnoses. Where limited resources create a challenge for testing everyone with a new suspected diagnosis of asthma, those with an intermediate probability should be prioritised for spirometry and also FENO where available.
Date for review: 23rd October 2025
A new report is showcasing the impact of a national AHSN Network programme to improve access to FeNO testing for asthma diagnosis. Fractional exhaled Nitric Oxide (FeNO) tests are simple, non-invasive tests to support the diagnosis of asthma. During the two-year programme an estimated 58,000 new asthmatics received a faster, more accurate diagnosis through the use of FeNO testing with an additional 1,200 devices entering use in primary care in England.
To consider how and when we use FeNO testing, we need to go to the definition of asthma. Both BTS/SIGN1 and GINA2 define it as a predominantly inflammatory disorder of the airways with airway hyperresponsiveness and variability in symptoms. Nitric oxide is a gas involved in the respiratory process and is present in the atmosphere in very small amounts (parts per billion). It can be easily measured in exhaled breath using a fractional exhaled nitric oxide (FeNO) test.