From the Guidelines
Diagnosing asthma requires a comprehensive approach that includes a detailed medical history, physical examination, and spirometry testing to assess airflow obstruction and reversibility, as recommended by the expert panel report 3 (EPR-3) guidelines 1. To establish a diagnosis of asthma, the following key steps should be taken:
- Determine the presence of episodic symptoms of airflow obstruction or airway hyperresponsiveness, such as cough, wheeze, difficulty breathing, or chest tightness, which may worsen at night or during exercise 1.
- Assess airflow obstruction using spirometry, which measures the forced expiratory volume in one second (FEV1) before and after inhalation of a short-acting beta-2 agonist (SABA), with a significant improvement in lung function indicating asthma 1.
- Consider alternative causes of airway obstruction and perform additional tests, such as peak flow monitoring, bronchoprovocation testing, or allergy testing, if necessary 1.
- For children under 5, diagnosis relies more heavily on symptom patterns and response to trial asthma medications, as they often cannot perform reliable spirometry 1. The diagnosis of asthma should be based on a combination of these factors, rather than relying solely on medical history or physical examination, as the disease can be variable and signs may be absent between episodes 1.
From the Research
Diagnosing Asthma
To diagnose asthma, a combination of clinical assessment and diagnostic testing is used. The symptoms of asthma include:
Clinical Assessment
The physical exam can demonstrate:
- Hyperinflation
- Wheezing
- Increased work of breathing However, most patients will present with a normal pulmonary exam because they are between episodes 2.
Diagnostic Testing
Diagnostic testing, such as spirometry with bronchodilator response (BDR) or methacholine challenge testing (MCT), is essential to confirm the diagnosis of asthma 3, 5, 6.
- Spirometry measures the amount and speed of air that can be inhaled and exhaled by the lungs.
- Methacholine challenge testing measures the airway responsiveness to methacholine, a substance that can trigger airway constriction.
Factors Affecting Diagnosis
The diagnosis of asthma can be affected by:
- Age: Diagnosis of asthma in the pediatric population may be more difficult because the classic symptoms may not be present in many of those patients 2.
- Medication: Controller medication tapering can affect MCT results, and temporal variability can occur over time 6.
- Clinical correlation: Clinical correlation with spirometry and other diagnostic testing is essential to establish a diagnosis of asthma 4.
Diagnostic Approach
The diagnosis of asthma is made in the setting of clinical history, physical exam, and diagnostic testing 2. A negative BDR test does not exclude asthma, and repeat testing may be warranted in patients with a high clinical suspicion of asthma 6.