What is the practical approach to diagnosing Reactive Airway Disease (RAD) in an infant or preschool‑aged child who presents with episodic wheezing, cough, shortness of breath, or chest tightness that improves with a short‑acting bronchodilator?

Diagnosing Reactive Airway Disease in Infants and Preschool Children

When an infant or preschool-aged child presents with episodic wheezing, cough, shortness of breath, or chest tightness that improves with a short-acting bronchodilator, the diagnosis of reversible airway disease (asthma) can be made clinically without pulmonary function testing. 1

Clinical Diagnosis Framework

Direct Observation of Bronchodilator Response

• If you directly observe acute wheeze that responds to a bronchodilator, pulmonary function testing is not needed for diagnosis. 1
• The American Thoracic Society/European Respiratory Society explicitly states that when a child presents with acute wheeze and is observed to respond to a bronchodilator, there is little doubt that symptomatic reversible airway disease exists, and this should be called asthma. 1
• In this clinical scenario, the diagnosis is established by the therapeutic response itself. 1

Terminology Considerations

• Use the term "asthma" rather than "reactive airway disease" (RAD) to facilitate clear communication and timely treatment. 2
• Research demonstrates that children diagnosed with RAD receive action plans and controller medications on average 9 months later than those diagnosed with asthma, despite having identical clinical outcomes at 2 years. 2
• RAD diagnoses are linked to delayed delivery of preventive care measures including controller medications and asthma action plans. 2

When Clinical Diagnosis is More Challenging

Vague or Intermittent Symptoms

• Diagnosis becomes difficult when the child presents with vague symptoms (cough or shortness of breath) and physical examination is normal at the time of evaluation. 1
• Mild intermittent asthma is often wrongly diagnosed, with the main alternative diagnosis being persistent isolated cough. 1
• In these cases, clinical judgment must be complemented by tests of atopic status (such as family history of asthma, personal history of atopic dermatitis, or elevated eosinophils). 1

Role of Pulmonary Function Testing in Preschool Children

Pulmonary function testing has significant limitations in this age group:

• Baseline pulmonary function tests have very poor diagnostic accuracy due to great overlap between healthy children and those with previous wheeze. 1
• Bronchodilator responsiveness testing (BDR) provides better diagnostic profiles than baseline measurements, but still has substantial false-positive rates. 1
• In children aged 2-5 years, a BDR ratio (baseline Rint:post-bronchodilator Rint) of ≥1.22 has 76% sensitivity but only 70% specificity, meaning 30% of healthy children will test positive. 1
• Spirometry has poor diagnostic profiles in young children due to overlap between those with and without lung disease. 1

Practical Diagnostic Algorithm for Infants and Preschoolers

Step 1: Document Clinical Features

• Record the specific respiratory symptoms: episodic wheeze (most specific), cough, shortness of breath, chest tightness. 3
• Document frequency and severity: number of episodes, duration, sleep disruption, activity limitation. 3
• Assess atopic risk factors: parental asthma, physician-diagnosed atopic dermatitis, allergic rhinitis. 3

Step 2: Trial of Short-Acting Bronchodilator

• Administer albuterol via metered-dose inhaler with spacer and face mask (preferred delivery method for children under 4 years). 1, 3
• Observe for clinical improvement in wheeze, work of breathing, and respiratory distress within 15-20 minutes. 1, 3
• If clear symptomatic improvement occurs, the diagnosis of reversible airway disease is established. 1

Step 3: Consider Alternative Diagnoses if No Response

• Lack of clinical improvement after 2 weeks of bronchodilator therapy should raise suspicion for alternative diagnoses. 3
• Important differentials include:
  • Anatomic abnormalities (tracheomalacia, bronchomalacia, vascular rings): present in approximately 33% of children with persistent wheezing. 3
  • Aspiration: detected in 10-15% of children with respiratory symptoms on videofluoroscopic swallow studies. 3
  • Gastroesophageal reflux: present in 47-100% of children with persistent wheezing on 24-hour pH monitoring. 3
  • Bacterial infection: positive bronchoalveolar lavage cultures in 40-60% of persistent wheezers. 3

Step 4: Criteria for Long-Term Controller Therapy

Consider initiating inhaled corticosteroids if the child meets ALL of the following:

• ≥3 wheezing episodes in the past year that each lasted >1 day and affected sleep. 3
• PLUS at least one major risk factor:
  • Parental history of asthma
  • Physician-diagnosed atopic dermatitis
  • Severe exacerbations requiring β₂-agonist use more frequently than every 4 hours over 24 hours
  • Emergency department visits or hospitalizations for wheezing. 3

Critical Pitfalls to Avoid

Overdiagnosis Based on Upper Airway Sounds

• Positional "wheezing" that resolves with position changes represents stertor (upper airway noise), not true lower airway obstruction. 4
• True wheezing from bronchospasm does not resolve with positional changes alone. 4
• Normal weight and growth percentiles argue strongly against chronic aspiration or other pathologic causes. 4
• Do not initiate bronchodilator or inhaled corticosteroid therapy based solely on positional sounds in an otherwise healthy infant. 4

Inappropriate Use of Nebulizers

• Overuse of nebulizers should be avoided as they are expensive, time-consuming, and often inefficient compared to metered-dose inhalers with large volume spacers. 3
• Every child given inhaled medications should use a large volume spacer to enhance lung deposition. 3

Delayed Recognition of Structural Abnormalities

• Beta-agonists may adversely affect airway dynamics in infants with tracheomalacia or bronchomalacia, making identification of these conditions important. 3
• Consider flexible fiberoptic bronchoscopy for persistent wheezing despite appropriate therapy, as anatomic abnormalities are found in approximately 33% of cases. 3
• Minor procedural complications (transient hypoxemia) occur in only 5-10% of bronchoscopy cases. 3

Failure to Provide Asthma Action Plans

• Most children initially diagnosed with RAD receive action plans and controller medications only after a subsequent asthma diagnosis, on average 9 months after their index visit. 2
• Provide written asthma action plans at the time of diagnosis, not after subsequent exacerbations. 2

Special Population: Preterm Infants

• A therapeutic trial of short-acting β₂-agonists can be considered even in preterm infants, though their response may differ from full-term infants. 1, 3
• In one study of 17 infants with bronchopulmonary dysplasia, 55% of those with recurrent wheeze responded to albuterol, compared with only 12.5% without wheezing. 1
• Monitor for tachycardia, transient drops in oxygen saturation, and tremor as the most frequently reported side effects. 3