What are the diagnostic criteria for bronchial asthma?

Diagnostic Criteria for Bronchial Asthma

The diagnosis of bronchial asthma requires a compatible clinical history of episodic respiratory symptoms AND objective confirmation of variable expiratory airflow limitation through pulmonary function testing. 1

Core Diagnostic Components

1. Clinical History Assessment

• Episodic respiratory symptoms that vary over time and intensity
• Symptoms often worse at night or early morning
• Triggers may include exercise, allergens, irritants, or viral infections
• Common symptoms: wheezing, chest tightness, shortness of breath, cough

2. First-Line Objective Testing (Essential)

The European Respiratory Society (ERS) recommends a combination of the following tests 2:

• Spirometry with bronchodilator reversibility testing

  • Demonstration of airflow obstruction (FEV₁/FVC ratio below lower limit of normal)
  • Positive bronchodilator response: increase in FEV₁ of ≥12% and ≥200 mL after bronchodilator administration 1

• Fractional exhaled nitric oxide (FeNO) measurement

  • Values ≥45-50 ppb suggest eosinophilic inflammation 1
  • Particularly useful in atopic asthma

• Peak Expiratory Flow (PEF) monitoring

  • Excessive variability in twice-daily PEF measurements over 2 weeks
  • Diurnal variation >20% over 1-2 weeks indicates asthma 1

3. Second-Line Testing (When First-Line Tests Are Inconclusive)

• Bronchial challenge testing (direct or indirect)
  • Direct challenges (methacholine): positive if ≥20% fall in FEV₁ at standard dose
  • Exercise challenge: positive if >10% fall in FEV₁ from baseline 2
  • Mannitol challenge: positive if ≥15% fall in FEV₁ from baseline or 10% decrease between consecutive doses 2

Diagnostic Algorithm

1. Initial Assessment:

   • Evaluate clinical history for characteristic asthma symptoms
   • Perform spirometry with bronchodilator reversibility testing
   • Measure FeNO levels

2. If Initial Tests Confirm Diagnosis:

   • Positive bronchodilator reversibility test (≥12% and ≥200 mL increase in FEV₁)
   • OR documented variability in lung function between visits
   • Diagnosis of asthma is confirmed

3. If Initial Tests Are Inconclusive:

   • Proceed to PEF monitoring over 2 weeks
   • If still inconclusive, consider bronchial challenge testing
   • For patients with exercise-related symptoms, consider exercise challenge testing 2

4. For Patients Already on Treatment:

   • Repeat objective lung function measures
   • Consider trial step-down of ICS-containing treatment to assess underlying condition 2

Important Considerations and Pitfalls

• Avoid diagnosis based solely on clinical history: Relying on symptoms without objective confirmation leads to misdiagnosis 1, 3

• Consider timing of testing: Tests performed during asymptomatic periods may be falsely negative; repeated testing may be necessary 1

• Beware of overdiagnosis: Systematic evaluation and complete pulmonary function testing are essential to avoid misdiagnosing other pulmonary conditions as asthma 4

• Single-point testing may miss asthma: Due to its variable nature, repeated testing over time may be necessary 1

• Differential diagnosis: Consider other conditions that may present with similar symptoms (COPD, vocal cord dysfunction, heart failure, etc.)

• Avoid using "reactive airway disease" as placeholder: This delays proper diagnosis and treatment 1

• Recognize that symptoms correlate poorly with airway obstruction in one-third to one-half of asthmatic patients 3

By following this structured approach to diagnosis that combines clinical assessment with objective testing, clinicians can accurately diagnose bronchial asthma and distinguish it from other respiratory conditions with similar presentations.