DIAGNOSTIC TRIAD

1. SYMPTOMS

   Wheeze, breathlessness, chest tightness, cough

2. VARIABLE AIRFLOW OBSTRUCTION

3. EOSINOPHILIC AIRWAY INFLAMMATION or ATOPY

OTHER FEATURES THAT INCREASE PROBABILITY OF ASTHMA DIAGNOSIS

1. Triggers: recurrent wheeze with exercise, viral infection, cold air, allergens, emotion/laughter, NSAIDs/Beta-blockers

2. Variability of recorded PEF and FEV1: lower values when symptomatic compared with asymptomatic

3. Personal history of atopy: eczema/dermatitis/allergic rhinitis, raised allergen-specific IgE levels, positive skin-prick tests to aeroallergens or blood eosinophilia

4. Diurnal symptom variability: worse at night/early morning

OBJECTIVE TESTS OF ASTHMA

VARIABLE AIRFLOW OBSTRUCTION

Peak expiratory flow (PEF) charting of variability
More than 20% variability in multiple daily PEF recordings (≥2) is regarded as a positive result for the diagnosis of asthma.

Occupational asthma: serial peak flow four times a day for three weeks at home and at work is a diagnostic test of proven value.
Suitable record forms can be downloaded from http://www.occupationalasthma.com.   

Spirometry with Bronchodilator reversibility (BDR) [PREFERRED INITIAL TEST]
May be performed in children aged>5yr
Obstructive spirometry diagnosed if FEV1/FVC ratio less than 70%.
Bronchodilator Reversibility: an improvement in FEV1 ≥ 12% in response to beta-2 agonists or corticosteroids is regarded as a positive result

Challenge Test: direct bronchial challenge test with histamine or methacholine
A PC20 value (provocative concentration causing a 20% drop in FEV1) of 8 mg/ml or less is regarded as a positive result.

EOSINOPHILIC AIRWAY INFLAMMATION or ATOPY

Fractional exhaled nitric oxide (FeNO) testing
Confirms eosinophilic airway inflammation
Test deemed positive (abnormal) if FeNO level ≥40 ppb in steroid-naive adults OR FeNO level ≥35 ppb in children
Approximately 1 in 5 people with a negative FeNO will have asthma (20% False-negative rate)
Approximately 1 in 5 people with a positive FeNO will not have asthma (20% False-positive rate)

Blood tests
Positive if blood eosinophilia ≥ 4%
Raised allergen-specific IgE

MANAGEMENT

1. HIGH PROBABILITY OF ASTHMA based on symptoms, variability and atopy:

Code as suspected asthma and initiate 6w inhaled corticosteroids + reliever B2 agonist

Monitor and assess response:
Spirometry FEV1/ at clinic visits
Validated symptom questionnaire
Domiciliary serial PEFs with/without symptoms

If good response, asthma diagnosis confirmed and will need adjustment of maintenance dose, self-management advice and on-going monitoring

2. INTERMEDIATE PROBABILITY OF ASTHMA

Undertake OBJECTIVE TESTS OF ASTHMA: variable airflow obstruction (e.g. spirometry with bronchodilator reversibility) AND eosinophilic airway inflammation

Red-flag signs suggesting alternative diagnosis and referral to a respiratory physician

Adults

• Severe/life-threatening asthma attack

• Prominent systemic features (such as myalgia, fever, and weight loss)

• Unexpected clinical findings (such as crackles, finger clubbing, cyanosis, evidence of cardiac disease, monophonic wheeze, or stridor).

• Persistent non-variable breathlessness

• Chronic sputum production

• Unexplained restrictive spirometry

• Chest X-ray shadowing

• Marked blood eosinophilia

• Suspected occupational asthma (symptoms improve away from work) in high-risk occupations

Children

• Failure to thrive

• Unexplained clinical findings (such as focal signs, abnormal voice or cry, dysphagia, and/or inspiratory stridor)

• Symptoms that are present from birth or perinatal lung problem

• Excessive vomiting or posseting

• Severe upper respiratory tract infection

• Persistent wet or productive cough

• Family history of unusual chest disease

• Nasal polyps

Differential diagnosis

• Bronchiectasis: copious sputum, frequent chest infections, a history of childhood pneumonia, and coarse lung crepitations

• Chronic obstructive pulmonary disease (COPD): asthma and COPD can be difficult to distinguish clinically and may co-exist. Clinical features of COPD include a productive cough and dyspnoea on exertion in a person over 35 years of age who is a current or previous smoker.

• Ciliary dyskinesia: persistent moist cough present from birth.

• Cystic fibrosis: persistent moist cough and gastrointestinal symptoms from birth, and failure to thrive in children.

• Dysfunctional breathing: breathlessness, dizziness, light-headedness, and peripheral tingling.

• Foreign body aspiration: sudden-onset cough, stridor (upper airway) or reduced chest wall movement on the affected side, bronchial breathing, and reduced or diminished breath sounds (lower airway).

• Gastro-oesophageal reflux: cough, postural and food-related symptoms, and vomiting

• Heart failure: orthopnoea, oedema, history of ischaemic heart disease, and fine lung crepitations

• Interstitial lung disease: asbestosis, pneumoconiosis, fibrosing alveolitis, sarcoidosis — dry cough and fine lung crepitations

• Lung cancer: cough, haemoptysis, weight loss, or persistent hoarse voice

• Pertussis: paroxysms of coughing, vomiting after coughing, or an inspiratory whoop, cough may persist for several months

• Pulmonary embolism (PE): acute-onset breathlessness, pleuritic pain, haemoptysis, crackles, and sinus tachycardia

• Tuberculosis: persistent productive cough, which may be associated with breathlessness and haemoptysis.

• Upper airway cough syndrome: frequent throat clearing and chronic sinusitis or allergic rhinitis

• Vocal cord dysfunction: dyspnoea and stridor