asthma

diagnosis in adults

Spirometry is the preferred initial test to assess the presence and severity of airflow obstruction
PEFR testing: PEF should be recorded as the best of three forced expiratory blows from total lung capacity with a maximum pause of two seconds before blowing. The patient can be standing or sitting. Further blows should be done if the largest two PEF are not within 40 l/min.

More than one of the following symptoms: wheeze, breathlessness, chest tightness and cough, particularly if:
- symptoms worse at night and in the early morning
- symptoms in response to exercise, allergen exposure and cold air
- symptoms after taking aspirin or beta blockers
History of atopic disorder
Family history of asthma and/or atopic disorder
Widespread wheeze heard on auscultation of the chest
Otherwise unexplained low FEV1 or PEF (historical or serial readings)
Otherwise unexplained peripheral blood eosinophilia

Prominent dizziness, light-headedness, peripheral tingling
Chronic productive cough in the absence of wheeze or breathlessness
Repeatedly normal physical examination of chest when symptomatic
Voice disturbance
Symptoms with colds only
Significant smoking history (ie >20 pack-years)
Cardiac disease
Normal PEF or spirometry when symptomatic
- NB. a normal spirogram/spirometry when not symptomatic does not exclude the diagnosis of asthma. Repeated measurements of lung function are often more informative than a single assessment.

if airway obstruction present:
- if spirometry/PEFR indicate airway obstruction (FEV1 / FVC < 0.7) but Dx of asthma is only intermediate probability:
  - test for reversibility of obstruction or commence a trial of SABA with oral prednisolone 30 mg daily for two weeks, and if beneficial, Rx as for asthma
    - a >400 ml improvement in FEV1 to either β2 agonists or corticosteroid treatment trials strongly suggests underlying asthma
    - but if not trial not beneficial, Ix for other causes of airway obstruction such as:
      - chronic obstructive pulmonary disease (COPD)
      - bronchiectasis
      - inhaled foreign body
      - obliterative bronchiolitis
      - large airway stenosis
      - lung cancer
      - sarcoidosis
if no evidence of airway obstruction (FEV1 / FVC > 0.7)
- if Dx of asthma is only intermediate probability, then refer for further Ix such as:
  - tests of airway responsiveness:
    - Methacholine PC20 challenge (the provocative concentration of methacholine required to cause a 20% fall in FEV1)
    - exercise challenge in untreated patients
  - tests for eosinophilic airway inflammation:
    - FENO (exhaled nitric oxide concentration)
    - Sputum eosinophil count
  - consider DDx such as:
    - Chronic cough syndromes
    - Hyperventilation syndrome
    - Vocal cord dysfunction
    - sinusitis
    - Gastro-oesophageal reflux
    - Heart failure
    - pulmonary fibrosis

see acute asthma in the adult patient for severe acute attacks requiring ED presentations

for example:
- exacerbations of asthma within past 2 years
- symptomatic or needing to use SABA 3x a week or more
- waking more than one night a week due to asthma
add a low dose inhaled corticosteroids preventer (ICS) such as (adult doses provided):
- beclometasone 200mcg bd (eg. QVar)
- budesonide 200mcg bd (eg. Pulmicort)
- fluticasone 125mcg bd (eg. Flixotide)
- mometasone 100mcg bd
- ciclesonide 100mcg bd
for those unable to use ICS, consider:
- sodium cromoglicate which is of some benefit in adults and is effective in children aged 5-12, or,
- leukotriene receptor antagonists have been shown to have some beneficial clinical effect
  - especially useful for children under 5 years