From the Guidelines
Determining if a patient has asthma involves a comprehensive evaluation of symptoms, medical history, physical examination, and diagnostic tests, with spirometry being a crucial diagnostic tool, as recommended by the most recent and highest quality study 1. To diagnose asthma, assess for characteristic symptoms including wheezing, shortness of breath, chest tightness, and coughing, particularly if these symptoms worsen at night or with triggers like exercise, allergens, or cold air.
- Key indicators of a diagnosis of asthma include:
- Wheezing
- History of recurrent cough, wheezing, difficulty in breathing, or chest tightness
- Symptoms that occur or worsen in the presence of specific triggers, such as exercise, allergens, or cold air Perform pulmonary function tests, specifically spirometry, which measures airflow before and after administering a bronchodilator like albuterol, as suggested by 1.
- A significant improvement in airflow (typically ≥12% and ≥200 mL increase in FEV1) after bronchodilator use supports an asthma diagnosis. For patients with normal spirometry but suspected asthma, bronchial challenge testing with methacholine or exercise can help identify airway hyperresponsiveness, as mentioned in 1.
- Peak flow monitoring over 1-2 weeks can detect variability in airflow characteristic of asthma. A thorough physical examination may reveal wheezing on auscultation, though patients can be symptom-free between exacerbations.
- Additional tests like chest X-rays, blood tests for eosinophil counts, and allergy testing can help rule out other conditions and identify potential triggers, as recommended by 1. The diagnosis of asthma is based on the pattern of symptoms, demonstration of variable airflow limitation, and exclusion of alternative diagnoses that might explain the symptoms, as emphasized by 1 and 1.
From the Research
Determining Asthma Diagnosis
To determine if a patient has asthma, the following steps can be taken:
- A thorough medical history is essential, as diagnostic tests can only increase or decrease the probability of an asthma diagnosis 2
- Spirometric evidence of airway obstruction plus a large bronchodilator response makes asthma more likely 2
- Inhalation challenge test can help confirm asthma in patients with normal spirometry 2
- Symptoms such as wheezing, chest tightness, and difficulty taking a deep breath suggest asthma, while symptoms like gasping, smothering, or air hunger suggest alternative diagnoses 3
- Respiratory signs like wheezing, breath sound intensity, and forced expiratory time can correlate roughly with airway obstruction, but clinicians may disagree on their presence or absence 3
Diagnostic Tests
The following diagnostic tests can be used to determine asthma:
- Spirometry to measure airway obstruction and bronchodilator response 2, 3
- Inhalation challenge test to confirm asthma in patients with normal spirometry 2
- Diffusing capacity of the lung for carbon monoxide to differentiate between asthma and COPD 2
- Exhaled nitric oxide level to diagnose allergic asthma 2
- Response to inhaled corticosteroids to confirm asthma diagnosis 2
Clinical Evaluation
Clinical evaluation of asthma involves:
- Medical history to identify symptoms and triggers 3, 4
- Physical examination to assess respiratory signs and symptoms 3
- Objective measures of lung function, such as spirometry, to accurately diagnose asthma 3, 4
- Classification of asthma severity using clinical history, spirometry, and symptom assessment 4