What are the diagnostic criteria and treatment options for a patient suspected of having asthma, presenting with recurrent respiratory symptoms such as wheezing, coughing, or shortness of breath?

Diagnosis of Asthma

Establish the Diagnosis Through Three Essential Components

Asthma diagnosis requires documenting characteristic variable respiratory symptoms combined with objective spirometry demonstrating reversible airflow obstruction in patients 5 years and older, while excluding alternative diagnoses. 1, 2

Clinical Features That Confirm Asthma

The diagnosis begins with identifying specific symptom patterns that distinguish asthma from other respiratory conditions:

• Recurrent episodes of wheezing, cough (particularly worse at night), shortness of breath, or chest tightness 1
• Variable and intermittent nature of symptoms—this variability is the clinical hallmark 1, 3
• Trigger-provoked symptoms including exercise, viral infections, allergens (animals with fur, dust mites, mold, pollen), irritants (tobacco smoke, chemicals), cold air, strong emotional expression, stress, or menstrual cycles 1, 4
• Nocturnal worsening with symptoms awakening the patient 1, 4

Critical caveat: Physical examination may be completely normal between episodes, and normal findings do not exclude asthma. 1, 4 During symptomatic periods, look for polyphonic bilateral wheezing (particularly expiratory), hyperinflation, use of accessory muscles, or hunched shoulders. 1

Objective Testing—The Diagnostic Cornerstone

Spirometry is mandatory for diagnosis in all patients 5 years and older because history and physical examination alone are unreliable for establishing the diagnosis or excluding other conditions. 1, 2

Spirometry Requirements:

• Measure FEV₁ and FEV₁/FVC ratio to document airflow obstruction 2, 4
• Document reversibility: FEV₁ improvement ≥12% AND ≥200 mL after bronchodilator administration 2, 4
• 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 1, 4

When Spirometry is Normal or Near-Normal:

• Bronchoprovocation testing with methacholine, histamine, cold air, or exercise challenge should be performed 1, 2
• A positive test confirms airway hyperresponsiveness (characteristic of asthma), while a negative test is more helpful to rule out asthma 1
• Must be performed only by trained personnel for safety reasons 1

Alternative Monitoring When Spirometry Unavailable:

• Peak expiratory flow (PEF) monitoring showing ≥20% variability in amplitude with minimum change of 60 L/min, ideally for 3 days per week over 2 weeks 1
• Caveat: PEF variability below 20% does not exclude asthma—this is a specific but insensitive test 1

Exclude Alternative Diagnoses

Before confirming asthma, systematically exclude other conditions:

In Children:

• Foreign body in trachea or bronchus 1, 2
• Vocal cord dysfunction 1, 2
• Vascular rings or laryngeal webs 1, 2
• Aspiration from swallowing dysfunction or gastroesophageal reflux 1, 2

In Adults:

• COPD (chronic bronchitis or emphysema)—consider diffusing capacity testing to differentiate 1, 2
• Congestive heart failure 1, 2
• Pulmonary embolism 1, 2
• Mechanical airway obstruction (benign and malignant tumors) 1
• Cough secondary to ACE inhibitors 1, 2
• Vocal cord dysfunction—evaluate inspiratory flow-volume loops 1

Chest radiography may be needed to exclude other pathology, though normal findings between episodes do not exclude asthma. 1, 2

Additional Diagnostic Considerations

Supporting Historical Features:

• Personal or family history of asthma, eczema, or allergic rhinitis 1, 4
• Worsening after aspirin/NSAIDs or beta-blocker use 1

Special Asthma Presentations:

• Cough variant asthma: Cough is the principal or only manifestation, especially in young children 1
• Diagnosis still requires objective confirmation of airway hyperresponsiveness 1

Comorbid Conditions to Assess:

• GERD, obstructive sleep apnea, and allergic bronchopulmonary aspergillosis may coexist and complicate diagnosis 2, 5

Diagnostic Algorithm Summary

1. Document characteristic symptoms: Variable, intermittent, trigger-provoked, nocturnal worsening 1, 2
2. Perform spirometry (age ≥5 years): Demonstrate obstruction and reversibility (FEV₁ ≥12% and ≥200 mL improvement) 2, 4
3. If spirometry normal but suspicion high: Bronchoprovocation testing 1, 2
4. Exclude alternatives: Chest X-ray, consider additional pulmonary function studies based on clinical context 1, 2
5. Assess for comorbidities that may complicate management 2, 5

Common pitfall: Do not diagnose asthma based on symptoms alone without objective testing, as this leads to misdiagnosis and inappropriate treatment. 1, 2