What is the recommended approach to diagnose asthma in children older than six years?

Diagnosing Asthma in Children Older Than 6 Years

Asthma diagnosis in children aged 6-16 years requires objective testing and cannot be made on symptoms alone—use spirometry, FeNO measurement, and bronchodilator reversibility testing as first-line diagnostic tests, with at least two positive objective tests needed to confirm the diagnosis. 1

Core Diagnostic Principle

The 2021 European Respiratory Society guidelines provide the most comprehensive, evidence-based approach for this age group. Never diagnose asthma based solely on clinical symptoms (strong recommendation against, moderate quality evidence). 1 While recurrent wheeze, cough, and breathing difficulty are key symptoms, they lack sufficient specificity—wheeze sensitivity ranges only 0.55-0.86 and specificity 0.64-0.90. 1

First-Line Objective Tests (Perform These Initially)

1. Spirometry (Strong Recommendation)

• Perform in all children aged 5-16 years with suspected asthma 1
• Consider supportive of asthma if:
  • FEV₁/FVC <LLN or <80%, OR
  • FEV₁ <LLN or <80% predicted
• Critical caveat: Normal spirometry does NOT exclude asthma 1
• Be aware that some children cannot perform adequate FVC maneuvers, potentially causing false-normal FEV₁/FVC ratios 1

2. FeNO Measurement (Strong Recommendation)

• Perform as part of initial diagnostic work-up 1
• FeNO ≥25 ppb in symptomatic children supports asthma diagnosis
• Important limitation: FeNO <25 ppb does NOT exclude asthma 1

3. Bronchodilator Reversibility (BDR) Testing

• Strongly recommended in all children with abnormal spirometry (FEV₁ <LLN or <80% predicted and/or FEV₁/FVC <LLN or <80%) 1
• Positive test: FEV₁ increase ≥12% AND/OR ≥200 mL following 400 μg SABA
• Most task force members also perform BDR when baseline spirometry is normal if clinical history strongly suggests asthma 1
• Key point: BDR <12% does NOT exclude asthma 1

Diagnostic Algorithm

Step 1: Child presents with recurrent wheeze, cough, or breathing difficulty

• Perform: Spirometry + FeNO measurement

Step 2: Interpret initial tests

• If spirometry shows obstruction (FEV₁/FVC or FEV₁ <LLN or <80%):

  • Perform BDR testing immediately
  • If BDR positive (≥12% increase) + FeNO ≥25 ppb = Asthma confirmed
  • If BDR negative but FeNO ≥25 ppb = Consider medication trial (see below)

• If spirometry is normal:

  • If FeNO ≥25 ppb + strong clinical history = Consider BDR testing anyway
  • If both normal but strong clinical suspicion = Proceed to second-line tests

Step 3: Second-line tests (when first-line tests inconclusive)

Bronchial Challenge Testing

• Direct challenge (methacholine): Conditional recommendation for children where first-line tests didn't confirm diagnosis 1

  • PC₂₀ ≤8 mg/mL = positive test

• Indirect challenge (exercise testing): Conditional recommendation for children with exercise-related symptoms 1

  • Fall in FEV₁ >10% from baseline = positive test
  • Use treadmill or bicycle
  • Mannitol challenge is an alternative but less available

What NOT to Use for Diagnosis

Strongly recommended AGAINST:

• Symptoms alone (strong recommendation) 1
• Improvement after preventer medication trial alone (conditional recommendation) 1
• PEFR variability as primary test (conditional recommendation—only use if other tests unavailable) 1
• Allergy testing (skin prick or IgE) for asthma diagnosis (strong recommendation against) 1

Special Consideration: Medication Trial

Only consider a trial of preventer medication in this specific scenario:

• Symptomatic child with abnormal spirometry BUT negative BDR 1
• Repeat spirometry and BDR after 4-8 weeks
• Never use medication response alone to diagnose asthma 1

Critical Pitfalls to Avoid

1. Chronic cough as sole symptom: Children with cough >4 weeks as the ONLY symptom are unlikely to have asthma—investigate per chronic cough guidelines and consider alternative diagnoses 1

2. Single positive test trap: The guidelines emphasize needing doctor diagnosis PLUS at least one abnormal comparator test, but best practice requires multiple objective tests for confirmation 1

3. False reassurance from normal tests: Normal spirometry, negative BDR, or FeNO <25 ppb do NOT exclude asthma—proceed to challenge testing if clinical suspicion remains high 1

4. Misinterpreting wheeze: Parents often confuse stridor and rattles with wheeze; the term lacks equivalent translations in many languages 1

Practical Implementation

Real-world data shows 77% adherence to this approach is achievable across multiple clinics 2. Deviations occur due to:

• Practice-related factors (44%): Different obstruction criteria
• Patient-related factors (33%): Inability to perform spirometry
• Logistical factors (22%): Scheduling difficulties

The approach requires flexibility while maintaining the core principle: objective testing is mandatory, symptoms alone are insufficient.