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Overview

This guideline covers diagnosing, monitoring and managing asthma in adults, young people and children. It aims to improve the accuracy of diagnosis, help people to control their asthma and reduce the risk of asthma attacks. It does not cover managing severe asthma or acute asthma attacks. 

Initial clinical assessment

  • See Algorithm 1 below

initial assessment for suspected asthma

Algorithm 1: Initial clinical assessment for suspected asthma. Download a PDF of this algorithm

Clinical history 

  • Take a structured clinical history in people with suspected asthma. Specifically, check for: 
    • wheeze, cough or breathlessness, and any daily or seasonal variation in these symptoms 
    • any triggers that make symptoms worse 
    • a personal or family history of atopic disorders 
  • Do not use symptoms alone without an objective test to diagnose asthma  
  • Do not use a history of atopic disorders alone to diagnose asthma 

Physical examination 

  • Examine people with suspected asthma to identify expiratory polyphonic wheeze and signs of other causes of respiratory symptoms, but be aware that even if examination results are normal the person may still have asthma 

Initial treatment and objective tests for acute symptoms at presentation 

  • Treat people immediately if they are acutely unwell at presentation, and perform objective tests for asthma (for example, fractional exhaled nitric oxide [FeNO], spirometry and peak flow variability) if the equipment is available and testing will not compromise treatment of the acute episode 
  • If objective tests for asthma cannot be done immediately for people who are acutely unwell at presentation, carry them out when acute symptoms have been controlled, and advise people to contact their healthcare professional immediately if they become unwell while waiting to have objective tests 
  • Be aware that the results of spirometry and FeNO tests may be affected in people who have been treated empirically with inhaled corticosteroids 

Testing for asthma 

  • Do not offer the following as diagnostic tests for asthma: 
    • skin prick tests to aeroallergens 
    • serum total and specific IgE 
    • peripheral blood eosinophil count 
    • exercise challenge (to adults aged 17 years and over) 
  • Use skin prick tests to aeroallergens or specific IgE tests to identify triggers after a formal diagnosis of asthma has been made 

Occupational asthma 

  • Check for possible occupational asthma by asking employed people with suspected new-onset asthma, or established asthma that is poorly controlled: 
    • are symptoms better on days away from work? 
    • are symptoms better when on holiday?[A]
  • Make sure all answers are recorded for later review 
  • Refer people with suspected occupational asthma to an occupational asthma specialist 

Diagnosing asthma in young children

  • For children under 5 years of age with suspected asthma, treat symptoms based on observation and clinical judgement, and review the child on a regular basis. If they still have symptoms when they reach 5 years of age, carry out objective tests
  • If a child is unable to perform objective tests when they are aged 5 years: 
    • continue to treat based on observation and clinical judgement 
    • try doing the tests again every 6 to 12 months until satisfactory results are obtained 
    • consider referral for specialist assessment if the child repeatedly cannot perform objective tests and is not responding to treatment 

Objective tests for diagnosing asthma in adults, young people and children aged 5 years and over

objective tests for asthma in children and young people

Algorithm 2: Objective asthma assessment for children and young people. Download a PDF of this algorithm

objective tests for asthma in adults

Algorithm 3: Objective asthma assessment for adults. Download a PDF of this algorithm

See Table 1 for a summary of objective test threshold levels. 

Diagnostic hubs 

  • Those responsible for planning diagnostic service support to primary care (for example, clinical commissioning groups) should consider establishing asthma diagnostic hubs to achieve economies of scale and improve the practicality of implementing the recommendations in this guideline 

Airway inflammation measures 

Fractional exhaled nitric oxide 

  • Offer a FeNO test to adults (aged 17 years and over) if a diagnosis of asthma is being considered. Regard a FeNO level of 40 parts per billion (ppb) or more as a positive test 
  • Consider a FeNO test in children and young people (aged 5 to 16 years)[B] if there is diagnostic uncertainty after initial assessment and they have either: 
    • normal spirometry or 
    • obstructive spirometry with a negative bronchodilator reversibility (BDR) test

      Regard a FeNO level of 35 ppb or more as a positive test 
  • Be aware that a person’s current smoking status can lower FeNO levels both acutely and cumulatively. However, a high level remains useful in supporting a diagnosis of asthma 

Lung function tests

Spirometry

  • Offer spirometry to adults, young people and children aged 5 years and over if a diagnosis of asthma is being considered. Regard a forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) ratio of less than 70% (or below the lower limit of normal if this value is available) as a positive test for obstructive airway disease (obstructive spirometry) 

Bronchodilator reversibility

  • Offer a BDR test to adults (aged 17 years and over) with obstructive spirometry (FEV1/FVC ratio less than 70%). Regard an improvement in FEV1 of 12% or more, together with an increase in volume of 200 ml or more, as a positive test 
  • Consider a BDR test in children and young people (aged 5 to 16 years) with obstructive spirometry (FEV1/FVC ratio less than 70%). Regard an improvement in FEV1 of 12% or more as a positive test 

Peak expiratory flow variability

  • Monitor peak flow variability for 2  to 4 weeks in adults (aged 17 years and over) if there is diagnostic uncertainty after initial assessment and a FeNO test and they have either: 
    • normal spirometry or
    • obstructive spirometry, reversible airways obstruction (positive BDR) but a FeNO level of 39 ppb or less

      Regard a value of more than 20% variability as a positive test 
  • Consider monitoring peak flow variability for 2  to 4 weeks in adults (aged 17 years and over) if there is diagnostic uncertainty after initial assessment and they have: 
    • obstructive spirometry and
    • irreversible airways obstruction (negative BDR) and 
    • a FeNO level between 25 and 39 ppb

      Regard a value of more than 20% variability as a positive test 
  • Monitor peak flow variability for 2 to 4 weeks in children and young people (aged 5 to 16 years) if there is diagnostic uncertainty after initial assessment and a FeNO test and they have either: 
    • normal spirometry or
    • obstructive spirometry, irreversible airways obstruction (negative BDR) and a FeNO level of 35 ppb or more

      Regard a value of more than 20% variability as a positive test 

Airway hyperreactivity measures 

Direct bronchial challenge test with histamine or methacholine 

  • Offer a direct bronchial challenge test with histamine or methacholine[C] to adults (aged 17 years and over) if there is diagnostic uncertainty after a normal spirometry and either a: 
    • FeNO level of 40 ppb or more and no variability in peak flow readings or
    • FeNO level of 39 ppb or less with variability in peak flow readings

      Regard a PC20 value of 8 mg/ml or less as a positive test 
  • Consider a direct bronchial challenge test with histamine or methacholine[C] in adults (aged 17 years and over) with: 
    • obstructive spirometry without bronchodilator reversibility and 
    • a FeNO level between 25 and 39 ppb and 
    • no variability in peak flow readings (less than 20% variability over 2 to 4 weeks)

      Regard a PC20 value of 8 mg/ml or less as a positive test 
  • If a direct bronchial challenge test with histamine or methacholine is unavailable, suspect asthma and review the diagnosis after treatment, or refer to a centre with access to a histamine or methacholine challenge test 

Diagnosis in children and young people aged 5 to 16 years 

See also Algorithm 2 for objective asthma assessment for children and young people.

  • Diagnose asthma in children and young people (aged 5 to 16 years) if they have symptoms suggestive of asthma and: 
    • a FeNO level of 35 ppb or more and positive peak flow variability or
    • obstructive spirometry and positive bronchodilator reversibility 
  • Suspect asthma in children and young people (aged 5 to 16 years) if they have symptoms suggestive of asthma and: 
    • a FeNO level of 35 ppb or more with normal spirometry and negative peak flow variability, or 
    • a FeNO level of 35 ppb or more with obstructive spirometry but negative bronchodilator reversibility and no variability in peak flow readings, or 
    • normal spirometry, a FeNO level of 34 ppb or less and positive peak flow variability

      Do not rule out other diagnoses if symptom control continues to remain poor after treatment. Review the diagnosis after 6 weeks by repeating any abnormal tests and reviewing symptoms.
  • Refer children and young people (aged 5 to 16 years) for specialist assessment if they have obstructive spirometry, negative bronchodilator reversibility and a FeNO level of 34 ppb or less 
  • Consider alternative diagnoses and referral for specialist assessment in children and young people (aged 5 to 16 years) if they have symptoms suggestive of asthma but normal spirometry, a FeNO level of 34 ppb or less and negative peak flow variability 

Diagnosis in adults aged 17 years and over 

See also Algorithm 3 for objective asthma assessment for adults aged 17 years and over.

  • Diagnose asthma in adults (aged 17 years and over) if they have symptoms suggestive of asthma and: 
    • a FeNO level of 40 ppb or more with either positive bronchodilator reversibility or positive peak flow variability or bronchial hyperreactivity, or 
    • a FeNO level between 25 and 39 ppb and a positive bronchial challenge test, or
    • positive bronchodilator reversibility and positive peak flow variability irrespective of FeNO level 
  • Suspect asthma in adults (aged 17 years and over) with symptoms suggestive of asthma, obstructive spirometry and: 
    • negative bronchodilator reversibility, and either a FeNO level of 40 ppb or more, or a FeNO level between 25 and 39 ppb and positive peak flow variability, or
    • positive bronchodilator reversibility, a FeNO level between 25 and 39 ppb and negative peak flow variability

      Do not rule out other diagnoses if symptom control continues to remain poor after treatment. Review the diagnosis after 6 to 10 weeks by repeating spirometry and objective measures of asthma control and reviewing symptoms 
  • Consider alternative diagnoses, or referral for a second opinion, in adults (aged 17 years and over) with symptoms suggestive of asthma and: 
    • a FeNO level below 40 ppb, normal spirometry and positive peak flow variability, or 
    • a FeNO level of 40 ppb or more but normal spirometry, negative peak flow variability, and negative bronchial challenge test, or
    • obstructive spirometry with bronchodilator reversibility, but a FeNO level below 25 ppb, and negative peak flow variability, or
    • positive peak flow variability but normal spirometry, a FeNO level below 40 ppb, and a negative bronchial challenge test, or 
    • obstructive spirometry with negative bronchodilator reversibility, a FeNO level below 25 ppb, and negative peak flow variability (if measured) 

Diagnosis in people who are unable to perform an objective test 

For young children who cannot perform objective tests, see diagnosing asthma in young children.

  • If an adult, young person or child with symptoms suggestive of asthma cannot perform a particular test, try to perform at least two other objective tests. Diagnose suspected asthma based on symptoms and any positive objective test results 

Good clinical practice in asthma diagnosis 

  • Record the basis for a diagnosis of asthma in a single entry in the person’s medical records, alongside the coded diagnostic entry 

Diagnostic summary

  • Table 1 summarises the objective test threshold levels 
Table 1: Positive test thresholds for objective tests for adults, young people and children (aged 5 and over)
Test Population Positive result 

FeNO 

Adults 

40 ppb or more 

Children and young people 

35 ppb or more 

Obstructive spirometry 

Adults, young people and children 

FEV1/FVC ratio less than 70% (or below the lower limit of normal if this value is available) 

Bronchodilator reversibility (BDR) test 

Adults 

Improvement in FEV1 of 12% or more and increase in volume of 200 ml or more 

Children and young people 

Improvement in FEV1 of 12% or more 

Peak flow variability 

Adults, young people and children 

Variability over 20% 

Direct bronchial challenge test with histamine or methacholine 

Adults 

PC20 of 8 mg/ml or less 

Children and young people 

n/a 

Abbreviations: FeNO=fractional exhaled nitric oxide; FEV1=forced expiratory volume in 1 second; FVC=forced vital capacity; PC20=provocative concentration of methacholine causing a 20% fall in FEV1

Monitoring asthma control

  • Monitor asthma control at every review. If control is suboptimal:
  • Consider using a validated questionnaire (for example, the Asthma Control Questionnaire or Asthma Control Test) to monitor asthma control in adults (aged 17 years and over)
  • Monitor asthma control at each review in adults, young people and children aged 5 and over using either spirometry or peak flow variability testing
  • Do not routinely use FeNO to monitor asthma control
  • Consider FeNO measurement as an option to support asthma management in people who are symptomatic despite using inhaled corticosteroids. (This recommendation is from NICE’s diagnostics guidance on measuring fractional exhaled nitric oxide concentration in asthma)
  • Do not use challenge testing to monitor asthma control.
  • Observe and give advice on the person’s inhaler technique:
    • at every consultation relating to an asthma attack, in all care settings
    • when there is deterioration in asthma control
    • when the inhaler device is changed
    • at every annual review
    • if the person asks for it to be checked

Terms used in this guideline

Expiratory polyphonic wheeze

A wheeze is a continuous, whistling sound produced in the airways during breathing. It is caused by narrowing or obstruction in the airways. An expiratory polyphonic wheeze has multiple pitches and tones heard over different areas of the lung when the person breathes out

Inhaled corticosteroid (ICS) doses

ICS doses and their pharmacological strengths vary across different formulations. In general, people with asthma should use the smallest doses of ICS that provide optimal control for their asthma, in order to reduce the risk of side effects.

The full guideline contains the tables used to categorise the evidence base into low, moderate and high doses. The tables can be used as a guide for dosage in clinical practice, but should not be interpreted as a definitive statement of the relative potencies of the different inhaled steroids.

  • For adults aged 17 years and over:
    • less than or equal to 400 micrograms budesonide or equivalent would be considered a low dose
    • more than 400 micrograms to 800 micrograms budesonide or equivalent would be considered a moderate dose
    • more than 800 micrograms budesonide or equivalent would be considered a high dose.
  • For children and young people aged 16 years and under:
    • less than or equal to 200 micrograms budesonide or equivalent would be considered a paediatric low dose
    • more than 200 micrograms to 400 micrograms budesonide or equivalent would be considered a paediatric moderate dose
    • more than 400 micrograms budesonide or equivalent would be considered a paediatric high dose

Objective test to diagnose asthma

Tests carried out to help determine whether a person has asthma, the results of which are not based on the person’s symptoms, for example, tests to measure lung function or evidence of inflammation. There is no single objective test to diagnose asthma

Suspected asthma

Suspected asthma describes a potential diagnosis of asthma based on symptoms and response to treatment that has not yet been confirmed with objective tests

[A] ‘Holiday’ here means any longer time away from work than usual breaks at weekends or between shifts

[B] Children at the lower end of the age range may not be able to do the FeNO test adequately. In these cases, apply the principles in recommendation diagnosing asthma in young children

[C] At the time of publication (November 2017), histamine and methacholine did not have UK marketing authorisation for this use. The healthcare professional should follow relevant professional guidance, taking full responsibility for the decision to use this test. Informed consent should be obtained and documented. See the General Medical Council’s Prescribing guidance: prescribing unlicensed medicines for further information

© NICE 2020. Asthma diagnosis and monitoring. Available from: www.nice.org.uk/guidance/NG80. All rights reserved. Subject to Notice of rights.

NICE guidance is prepared for the National Health Service in England. All NICE guidance is subject to regular review and may be updated or withdrawn. NICE accepts no responsibility for the use of its content in this product/publication. 

Published date: .

Last updated: 12 February 2020.

NICE asthma guideline: diagnosis and monitoring