Diagnosis Overview

Asthma is:

• Symptoms due to intermittent, variable airway narrowing that is often triggered by environmental stimuli (e.g. exercise, cold air, allergens etc.)
• Reversible airflow obstruction measured by at least 1 of the following (For more information see Lung Function Assessments):
  • Acute bronchodilator reversibility (uncommonly positive i.e. insensitive)
  • Spontaneous variability in spirometry during clinic/surgery/lab visits
  • Airway hyperresponsiveness measured by bronchial provocation testing
  • Peak flow variability

There is a long list of alternate diagnosis that cause ‘asthma-like symptoms’ (Chung et al. 2014). For the full list, see Table 6 (pg. 356) of the 2014 International ATS / ERS Guidelines

A thorough assessment is critical. A confident diagnosis of asthma requires:

• A history compatible with the definition above
• Clinical questionnaires may be useful for screening, documentation for research purposes or objective measurement of changes
• Physical examination
  • Upper airway examination
  • Excludes alternate diagnoses
• Variable airflow obstruction (as above)
• Assessment for comorbidities, which may impact on symptom severity and perception as well as treatment responsiveness

Severe asthma is:

• The presence of uncontrolled asthma symptoms due to variable airflow obstruction despite being on optimal treatment (Chung et al. 2014). For more information see Severe Asthma – Overview
• Treatment will be a minimum of ICS and LABA, ±LTRA, ±intermittent or continuous oral corticosteroids. For more information see Medications – Overview

Determine if treatment is optimal:

• Poor adherence and inhaler technique explain the vast majority of poor control or ‘difficult-to-treat’ asthma (Engelkes et al. 2015)
• Assess adherence to medications
  • This may require several visits and should be performed at every visit
  • Multiple input is valuable: GP, Specialist, Asthma Educator, Pharmacists (although only practical where there is a case manager in the clinic)
  • Consider objective assessments (e.g. dosimeters)
• Assess inhaler technique
  • Useful instructional videos are available here

• Lung function testing to confirm variable obstruction as detailed above
  • Acute bronchodilator reversibility
  • Spontaneous variability in spirometry during clinic/surgery/lab visits
  • Airway hyperresponsiveness measured by bronchial provocation testing
  • Peak flow variability.

• ‘Standard lung function’ – spirometry pre- and post- bronchodilator, lung volumes, diffusing capacity. For more information see Lung Function Assessments
• Bronchial challenge test
• Chest X-ray

The following tools and tests may be used, based on the clinical assessment and results of the basic tests above.

• Peak flow diary (Boezen et al. 1994, Quanjer et al. 1997) For more information see Asthma Education
  • Day-to-day variability in healthy adults is < ±8% of the mean. g. for a mean PEF of 500LPM, variability beyond 460-540 LPM is abnormal.
  • Collect ≥2 weeks of daily recordings, discarding the first 3 days (learning effect)
  • Either bd or morning recordings may be taken
• Bronchoscopy (rarely necessary and mostly used for research purposes)
• Allergy testing: Skin prick testing or radioallergosorbent test (RAST)
• Blood assessment to rule out vasculitis

HRCT chest to assess for associated bronchiectasis, emphysema or another diagnosis that will impact on symptom severity. For more information see Imaging