What are the steps to diagnose childhood asthma?

Diagnosing Childhood Asthma: A Structured Approach

The diagnosis of childhood asthma requires objective testing with spirometry, bronchodilator reversibility (BDR), and fractional exhaled nitric oxide (FeNO) as first-line tests, with at least two abnormal test results needed to confirm the diagnosis. 1

Step 1: Clinical Assessment

• Evaluate for key symptoms, particularly wheeze, which has better sensitivity (55-86%) and specificity (64-90%) for asthma diagnosis compared to other symptoms 1
• Note that cough and breathing difficulty are nonspecific symptoms and should not be used alone to diagnose asthma 1
• Document symptom patterns, including frequency, triggers, and response to previous treatments 1
• Consider family history of atopic diseases and personal history of allergic conditions 2

Step 2: First-Line Objective Testing

• Spirometry testing:

  • Measure FEV1 and FEV1/FVC ratio 1
  • Abnormal results: FEV1 or FEV1/FVC less than lower limit of normal (LLN) and/or <80% predicted 1
  • Note that normal spirometry does not exclude asthma, and abnormal spirometry alone does not confirm it 1

• Bronchodilator reversibility (BDR) testing:

  • Perform even with normal spirometry if there is strong clinical suspicion 1
  • Positive BDR indicates reversible airflow obstruction characteristic of asthma 1

• Fractional exhaled nitric oxide (FeNO) testing:

  • Ideally performed before spirometry 1
  • Cut-off of 25 ppb is recommended based on recent evidence 1
  • Elevated levels suggest eosinophilic airway inflammation 1

Step 3: Additional Testing When Diagnosis Remains Unclear

• Peak expiratory flow rate (PEFR) variability:

  • Consider 2 weeks of twice-daily PEFR measurements 1
  • Variability >12% suggests asthma 1
  • Less reliable than other tests but useful when other testing is unavailable 1

• Bronchial challenge testing:

  • Consider direct (methacholine) or indirect (exercise) challenge testing when other tests are inconclusive 1, 3
  • Methacholine challenge is indicated for patients five years and older who do not have clinically apparent asthma 3
  • Positive test indicates bronchial hyperresponsiveness 1

• Allergy testing:

  • Skin testing can support an asthma diagnosis in preschool-aged children 4
  • Helps identify potential triggers but is not diagnostic on its own 4

Step 4: Diagnostic Decision Making

• Confirm diagnosis when:

  • At least two objective test results are abnormal 1
  • For example, abnormal spirometry plus positive BDR or elevated FeNO 1

• Consider watchful waiting when:

  • Initial tests are normal but clinical suspicion remains high 1
  • Repeat testing when the child is symptomatic 1

Important Caveats and Pitfalls

• Do not rely solely on symptoms for diagnosis:

  • Using symptoms alone results in misdiagnosis in many children 1
  • The combination of wheeze, breathlessness, chest tightness, and cough is reported in 71.26% of asthma cases but is not sufficient for diagnosis 5

• Avoid diagnosis based only on treatment response:

  • Do not diagnose asthma based solely on improvement in symptoms after a trial of preventer medication 1
  • A trial of medication can be considered only in symptomatic children with abnormal spirometry and negative bronchodilator response, with repeat objective testing after 4-8 weeks 1

• Rule out alternative diagnoses:

  • Consider conditions that mimic asthma (cystic fibrosis, foreign body aspiration) 6
  • Perform appropriate investigations to exclude these conditions 6, 2

• Consider age-appropriate approaches:

  • Diagnosis is more challenging in younger children 4
  • The ERS guidelines focus on children aged 5-16 years 1

By following this structured approach with emphasis on objective testing, clinicians can more accurately diagnose childhood asthma, leading to appropriate treatment and improved outcomes for affected children.