What are the diagnostic criteria and treatment options for a patient presenting with recurrent episodes of wheezing, coughing, chest tightness, or shortness of breath, suspected of having asthma?

Diagnosis of Asthma

Asthma diagnosis requires documenting characteristic variable symptoms (wheezing, shortness of breath, chest tightness, or cough) combined with objective spirometry demonstrating reversible airflow obstruction (FEV1 improvement ≥12% and ≥200 mL post-bronchodilator) in all patients 5 years and older. 1

Clinical Features That Establish Diagnosis

The symptom pattern is critical for identifying asthma and includes:

• Variable and intermittent symptoms including wheezing, shortness of breath, chest tightness, or cough 1, 2
• Trigger-provoked symptoms from exercise, allergens, viral infections, cold air, or irritants 2
• Nocturnal worsening of symptoms 1, 2
• Polyphonic wheezing with exercise is a cardinal sign 1

Critical caveat: Physical examination may be completely normal between episodes, and normal findings do not exclude asthma. 1, 2 This is a common pitfall—do not rely on physical examination alone to rule out asthma.

Essential Objective Testing

Spirometry (Required for Diagnosis)

• Spirometry is mandatory for all patients 5 years or older, as medical history and physical examination alone are unreliable for establishing diagnosis or excluding other conditions 1
• Measure FEV1 and FEV1/FVC ratio at baseline 1, 2
• Document reversibility: FEV1 improvement ≥12% AND ≥200 mL after bronchodilator administration 1
• Important limitation: Spirometry may be normal between episodes in mild asthma; if repeatedly normal despite symptoms, the diagnosis must be questioned but cannot be excluded based on this alone 2

Bronchoprovocation Testing (When Spirometry Normal or Unavailable)

• Use methacholine, histamine, cold air, or exercise challenge when spirometry is normal or unavailable 1
• A negative methacholine challenge is defined as FEV1 reduction <20% after all doses have been administered 3
• Beware false positives: Methacholine challenge may be falsely positive after influenza infection, upper respiratory infection, immunizations, in very young or very old patients, in patients with chronic lung disease, allergic rhinitis without asthma, smokers, or after exposure to air pollutants 3

Peak Expiratory Flow (PEF) Monitoring

• Use serial PEF measurements showing variability when spirometry is unavailable or normal 2

Medication Timing Before Testing

Hold these medications before bronchoprovocation testing to avoid false-negative results: 3

• Short-acting β-agonists (albuterol): 6 hours
• Long-acting β-agonists (salmeterol): 36 hours
• Short-acting anticholinergics (ipratropium): 12 hours
• Long-acting anticholinergics (tiotropium): ≥168 hours
• Oral theophylline: 12-48 hours

Note: Oral or inhaled corticosteroids and inhaled cromoglycate may decrease bronchial responsiveness but can be continued during testing 3

Differential Diagnosis to Exclude

In Children:

• Foreign body in trachea or bronchus 1
• Vocal cord dysfunction 1
• Vascular rings or laryngeal webs 1
• Aspiration from swallowing dysfunction or gastroesophageal reflux 1

In Adults:

• COPD 1, 2
• Congestive heart failure 1
• Pulmonary embolism 1, 2
• Mechanical airway obstruction 1
• Cough secondary to ACE inhibitors 1
• Vocal cord dysfunction 2
• Bronchiectasis 2

Additional Testing Considerations

• Chest radiography may be used to exclude other pathology, though a normal chest X-ray between episodes does not exclude asthma 1, 2
• Additional pulmonary function studies (diffusing capacity, lung volumes, inspiratory flow-volume loops) may be indicated in certain cases 1
• Screen for comorbid conditions including GERD, obstructive sleep apnea, and allergic bronchopulmonary aspergillosis, which may coexist with asthma and complicate diagnosis 1

Diagnostic Algorithm

1. Document characteristic symptom pattern (variable, intermittent, trigger-provoked, nocturnal worsening)
2. Obtain personal/family history of asthma, eczema, or allergic rhinitis 2
3. Perform spirometry with bronchodilator response in all patients ≥5 years
4. If spirometry shows FEV1 improvement ≥12% AND ≥200 mL post-bronchodilator → Diagnosis confirmed 1
5. If spirometry normal but symptoms persist → Perform bronchoprovocation testing or serial PEF monitoring 1, 2
6. Obtain chest radiography to exclude alternative diagnoses 1, 2
7. Consider comorbid conditions that may complicate presentation 1