How is asthma diagnosed and monitored, and what are the recommended medical interventions and laboratory tests?

Asthma Diagnosis and Monitoring

Diagnosis

Asthma is diagnosed by combining a compatible clinical history with objective confirmation of variable expiratory airflow limitation on pulmonary function testing—spirometry is essential and should not be skipped. 1, 2

Clinical Features to Identify

The diagnosis requires episodic symptoms where airflow obstruction is at least partially reversible and alternative diagnoses are excluded. 1 Key clinical indicators include:

• Symptom pattern: Wheeze, recurrent cough, difficulty breathing, or chest tightness that is variable, intermittent, worse at night, and provoked by specific triggers (exercise, allergens, cold air) 1
• Temporal patterns: Note whether symptoms are perennial, seasonal, continual, or episodic, with diurnal variations 1
• Family history: Asthma, allergy, or other atopic disorders in family members 1
• Associated conditions: Upper respiratory symptoms, skin findings suggesting atopy 1

Critical caveat: Clinical history and physical examination alone are unreliable for diagnosis—objective testing is mandatory to avoid the 30-35% overdiagnosis rate documented when physicians rely solely on symptoms. 3, 4

Objective Diagnostic Testing

Spirometry (for patients ≥5 years old) is the cornerstone of diagnosis and must be performed in all suspected cases. 1 The GINA guidelines specify five methods to objectively confirm excessive variability in lung function: 1, 2

1. Positive bronchodilator reversibility test: FEV₁ increase ≥12% AND ≥200 mL (or PEF increase ≥20% AND ≥60 L/min) from baseline 2
2. Excessive PEF variability: Documented over 2 weeks with twice-daily measurements 1, 2
3. Improvement after ICS trial: Increased lung function following 4 weeks of inhaled corticosteroid treatment 1, 2
4. Positive bronchial challenge test: Using methacholine, histamine, cold air, or exercise when spirometry is normal or near-normal 1, 2, 5
5. Excessive variation between visits: Documented variability in lung function over time 1, 2

Spirometry findings: Decreased FEV₁, decreased PEF, and reduced FEV₁/FVC ratio indicating obstructive pattern with reversibility 2

Special Diagnostic Situations

For patients already on ICS-containing medications who may not meet standard diagnostic criteria, repeat objective lung function measures and trial a step-down of ICS treatment to unmask reversible airflow limitation. 1, 2

Additional Testing

• Chest radiography: To exclude alternative diagnoses 1
• Allergy testing: To identify specific triggers and assess for allergic/eosinophilic phenotype 1, 2
• Exhaled nitric oxide or peripheral blood eosinophils: To identify eosinophilic phenotype, particularly important for severe asthma management 3

Monitoring

Assessment Framework

Once diagnosed, assess severity initially to guide treatment initiation, then monitor control over time to adjust therapy—these are separate assessments. 1 Both severity and control are classified using two domains:

1. Current impairment: Frequency and intensity of symptoms and functional limitations 1
2. Future risk: Likelihood of exacerbations, progressive lung function decline, or medication adverse effects 1

Impairment Domain Monitoring

Assess using these parameters (for patients ≥12 years): 1

• Symptom frequency: Days per week with symptoms
• Nighttime awakenings: Frequency per month
• SABA use for symptom relief: Days per week (not including pre-exercise use)
• Interference with normal activity: Degree of limitation
• Lung function: FEV₁ or PEF measurements

Classification levels: Intermittent (symptoms ≤2 days/week), Mild Persistent (>2 days/week but not daily), Moderate Persistent (daily symptoms), Severe Persistent (symptoms throughout the day) 1

Risk Domain Monitoring

• Exacerbation frequency: Number requiring oral systemic corticosteroids 1
• Progressive lung function decline: Serial spirometry measurements 1

Important principle: Patients at any severity level, including intermittent asthma, can experience severe exacerbations, so risk assessment is critical for all patients. 1

Ongoing Monitoring Tools

• Regular spirometry: For patients ≥5 years to track lung function over time 1
• Peak flow monitoring: Particularly useful for patients with poor symptom perception 1
• Symptom assessment: At each visit using standardized questions 1
• Medication review: Adherence, technique, and side effects 1

Severe Asthma Considerations

For the 5-10% with severe asthma (accounting for 50% of healthcare costs), monitoring should include: 1

• Referral to asthma specialists for comprehensive evaluation 1
• Asthma phenotyping using biomarkers: To assess eligibility for biologic therapies 1
• More frequent lung function testing: To detect progressive decline 1