From the Guidelines
A diagnosis of asthma should be based on a compatible clinical history and objectively confirmed variable expiratory airflow limitation on lung function testing, with diagnostic criteria including a positive bronchodilator responsiveness test with spirometry, excessive variability in twice-daily peak expiratory flow measurements, increase in lung function following treatment with inhaled corticosteroid, positive bronchial challenge test, and/or excessive variation in lung function between visits 1.
Diagnostic Criteria for Asthma
The diagnostic criteria for asthma include:
- Episodic symptoms of airflow obstruction or airway hyperresponsiveness
- Airflow obstruction that is at least partially reversible, measured by spirometry, with an increase in FEV1 of >200 mL and 12% from baseline measure after inhalation of short-acting b2-agonist (SABA) 1
- History of symptoms such as cough, recurrent wheeze, recurrent difficulty in breathing, and recurrent chest tightness
- Symptoms that occur or worsen in the presence of triggers such as exercise, viral infection, inhalant allergens, irritants, changes in weather, strong emotional expression, stress, and menstrual cycles
Recommended Diagnostic Tests
The recommended diagnostic tests for asthma include:
- Spirometry to demonstrate obstruction and assess reversibility
- Bronchodilator responsiveness testing to measure the response to short-acting b2-agonist (SABA)
- Peak expiratory flow (PEF) measurements to assess variability in lung function
- Bronchial challenge test to assess airway responsiveness
- Measurement of fractional exhaled nitric oxide (FeNO) to assess airway inflammation
Importance of Objective Diagnostic Tests
Objective diagnostic tests such as spirometry and bronchodilator responsiveness testing are essential to confirm a diagnosis of asthma, as they provide a reliable and accurate assessment of lung function and airway responsiveness 1. A proper diagnosis of asthma ensures that patients receive appropriate care for their actual condition, and helps to prevent inappropriate treatment and potentially dangerous health consequences.
From the Research
Diagnostic Criteria for Asthma
The diagnostic criteria for a positive asthma test result involve a combination of clinical symptoms and objective tests of lung function. The following are some of the key diagnostic criteria:
- Presence of symptoms such as cough, wheeze, breathlessness, and chest tightness 2
- Spirometry with bronchodilator reversibility testing to demonstrate airway obstruction and variability thereof 3, 4
- Methacholine challenge testing to assess airway hyperresponsiveness 3, 5, 6
- Peak expiratory flow (PEF) variability measurement to support the clinical diagnosis 5, 4
Objective Diagnostic Testing
Objective diagnostic testing for asthma consists of two components:
- Demonstration of airway obstruction using spirometry with bronchodilator reversibility testing 4
- Documentation of variability in degree of obstruction using repeated peak flow measurement or bronchial challenge testing 4
Predictors of a Positive Asthma Test Result
Several predictors of a positive asthma test result have been identified, including:
- Presence of wheezing or coughing due to allergens 6
- Prebronchodilator airflow limitation 3
- Difficulty walking several blocks 6
- Positive response to methacholine challenge testing 5
Diagnostic Tools
Several diagnostic tools are available for asthma, including:
- Spirometry with bronchodilator reversibility testing 2, 3, 4
- Methacholine challenge testing 3, 5, 6
- Peak expiratory flow (PEF) variability measurement 5, 4
- Fractional exhaled nitric oxide measurement to demonstrate eosinophilic inflammation 4
- Skin prick tests (SPT) with common aeroallergens to demonstrate atopy 5