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How to diagnose asthma in children
Take a structured clinical history. Consider if low, moderate or high suspicion of asthma.
Specifically check for:
- Wheeze, cough or breathlessness
- Daily or seasonal variation in these symptoms
- Any triggers that make symptoms worse
- A personal or family history of atopic disorders
- Food allergies
- Comorbidities, including rhinitis, chronic rhinosinusitis, acid reflux, obesity, obstructive sleep apnoea, anxiety
Examine to identify expiratory polyphonic wheeze and signs of other causes or respiratory symptoms. Remember asthmatics can have a normal examination when well. Observe for other signs including hyper-inflated chest, eczema and transverse nasal crease.
Suspected asthma under 5 years
- Treat symptoms based on observation and clinical judgement, and review the child on a regular basis.
- Consider a trial of moderate dose Inhaled Corticosteroids (ICS) for 8 weeks for children experiencing:
- asthma related symptoms 3 times a week or more
- night time waking
- symptoms uncontrolled on a Short Acting Beta Agonist (SABA)
- After 8 weeks stop ICS and continue to monitor child symptoms
- If symptoms did not resolve during trial of ICS, review if alternative diagnosis is likely
- If symptoms resolved then reoccurred within 4 weeks of stopping ICS, restart ICS at a lower dose as first line maintenance therapy
- If symptoms resolved but reoccurred beyond 4 weeks after stopping ICS, repeat the 8 week trial of moderate dose ICS
- If uncontrolled on low dose of ICS, consider addition of 4mg Montelukast at bedtime. Review within 4 to 8 weeks
- If uncontrolled on low dose ICS and Montelukast, stop Montelukast and refer to a specialist
- If they still have symptoms of asthma when they turn 5 years old then attempt objective testing. Asthma can be coded at that point if the criteria below are met. Until then, code as 'suspected asthma'.
Suspected asthma 5 to 16 years
Consider objective testing, following algorithm below.
Lung function tests for children over 5 years
Spirometry
- Offer spirometry if a diagnosis of asthma is being considered
- Regard a FEV1/FVC below the lower limit of normal as a positive test for obstructive airway disease (obstructive spirometry). Remember that in children and young people their lower limit of normal (LLN) is likely to be higher than 70% which is the threshold that has been used previously. For example, a ratio of 71% with a LLN of 73% indicates obstruction.
- Do a bronchodilator reversibility test for children and young people with obstructive spirometry
- Regard an improvement in FEV1 of 12% or more as a positive test
FeNO
- Offer Fractional Exhaled Nitric Oxide (FeNO) testing if there is diagnostic uncertainty and they have either:
- Normal spirometry or
- Obstructive spirometry with a negative bronchodilator reversibility test
- Regard a FeNO level of 35ppb or more as a positive test
- Be aware that if a child smokes, this can falsely lower FeNO levels. However, a high level remains useful in supporting a diagnosis of asthma
Peak expiratory flow variability
Monitor peak flow variability for 2 to 4 weeks in children and young people if there is diagnostic uncertainty and:
- Normal spirometry or
- Obstructive spirometry, irreversible airways obstruction (negative BDR) and a FeNO level of 35ppb or more
- FeNO is unavailable
Ask the child to take peak flow readings morning and evening for 2 - 4 weeks.
- To calculate PEFR variability using the daily amplitude percent mean method, you work out the variability for each day and then use that to find the average over the recording period
- Daily variability = Difference between highest and lowest peak flows / Average of highest and lowest
- Formula to calculate peak flow variability for each day: [(Highest - Lowest) / (Highest + Lowest) / 2] x 100 = Percentage variability
- Overall variability = Total of daily variabilities / Number of days
- Regard a value of more than 20% variability overall variability as a positive test.
- PEF charting when asthma is well controlled is unlikely to confirm variability
For further explanation and information about peak flows please visit PCRS peak flow consensus
Consider asthma in a child over 5 years if:
If the child is unable to perform objective testing
- Continue to treat based on observation and clinical judgement
- Try doing tests again every 6 to 12 months until satisfactory results obtained
- Consider referral to specialist if child repeatedly cannot perform objective tests and is not responding to treatment
When to diagnose asthma in children and young people aged 5 to 16 years
PDF: Objective tests for asthma in children and young people ages 5 to 16 years.
Code asthma after demonstrating any objective variability and a response to treatment.
Occasionally, symptoms subside independently, unrelated to the use of ICS. If no significant improvement is observed, cautiously discontinuing the ICS and advising parents to monitor the situation could be considered. Should symptoms reappear, instruct the parent to restart the ICS and inform you. If symptoms remain absent upon restarting, advise close monitoring by the parent, prompting them to report any recurrence. Providing parents with a peak flow meter for home use can aid in capturing variability during symptomatic periods.
FeNO testing and Spirometry may not be available in all areas of West Yorkshire. If there is clear peak flow variability and a response to treatment, this may suffice.
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.
Further information
Making the diagnosis of asthma in Children video presented by Dr Katharine Hickman, GP respiratory lead for West Yorkshire.
e-learning for healthcare: children and young people's asthma
References
Asthma: diagnosis, monitoring and chronic asthma management NICE guideline NG80, 2021
BTS/SIGN British guideline on the management of asthma: A national clinical guideline, 2019
Global Initiative for Asthma: Global Strategy for Asthma Management and Prevention, 2023