In a child with suspected bronchial asthma who has a normal chest X‑ray between attacks, which finding most supports the diagnosis of asthma?

Diagnosis of Asthma in Children with Normal Chest X-Ray Between Attacks

A normal chest X-ray between attacks (Option C) is the finding that most supports the diagnosis of asthma in this child, as chest radiography is typically normal in asthmatic children during symptom-free periods, and abnormalities appear only during acute exacerbations or when complications develop. 1, 2

Understanding the Diagnostic Value of Each Option

Normal Chest X-Ray Between Attacks (Option C)

This is the correct answer because it reflects the characteristic pattern of asthma:

• Chest X-rays in asthmatic children are routinely normal between attacks, with abnormalities appearing only during acute exacerbations or when complications such as pneumonitis, atelectasis, or air trapping develop 2
• The European Respiratory Society guidelines explicitly state that chest X-ray may be needed primarily to exclude other diagnoses rather than to confirm asthma 1
• During acute episodes, chest X-rays may show bilaterally increased air volume, low diaphragms, wide diaphragmatic angles, and increased peribronchial markings, but these findings resolve between attacks 2, 3
• The normalization of chest X-ray findings between episodes is consistent with the reversible airway obstruction that defines asthma 1

Polyphonic Wheeze on Exertion (Option B)

While wheeze is an important symptom in asthma diagnosis, this option has significant limitations:

• Wheeze does have reasonable diagnostic accuracy (sensitivity 55-86%, specificity 64-90%) for asthma 4
• However, the distinction between "exertion" and "exercise" in this option is artificial and clinically meaningless—both represent physical activity triggers 1
• More importantly, wheeze alone without objective testing is insufficient for diagnosis, as major guidelines recommend against diagnosing asthma based on symptoms alone in children who can perform objective tests 1, 4
• Polyphonic wheeze (multiple pitches heard simultaneously) indicates obstruction at multiple airway levels but is not specific to asthma and can occur in other conditions 1

Increased Risk of Upper Respiratory Infections (Option A)

This statement is factually incorrect:

• Asthma does not increase the risk of developing upper respiratory tract infections 1
• Rather, upper respiratory infections serve as triggers that worsen existing asthma symptoms—this is a well-recognized pattern in asthmatic children 1, 5
• The question stem itself notes that episodes worsen during URIs, which is a trigger pattern, not evidence of increased infection susceptibility

The Proper Diagnostic Approach in This Clinical Scenario

Age-Appropriate Testing Considerations

The child's age determines which objective tests can be performed:

• If the child is ≥5 years old, spirometry with bronchodilator reversibility testing and FeNO measurement should be performed as first-line objective tests 1, 4
• At least two abnormal objective test results are required to confirm asthma diagnosis in children aged 5-16 years 1, 4
• Children under 5-6 years cannot reliably perform spirometry or peak flow measurements, requiring a therapeutic trial approach instead 5, 6

Role of Chest X-Ray in Asthma Diagnosis

Chest radiography serves a specific but limited role:

• The primary purpose is to exclude alternative diagnoses such as foreign body aspiration, vascular rings, tumors, or structural abnormalities 1
• A normal chest X-ray between attacks supports (but does not confirm) asthma by ruling out chronic structural lung disease 2, 3
• Chest X-ray findings suggestive of lower airway obstruction (increased peribronchial markings, hyperinflation) may support diagnostic suspicion in younger children unable to perform spirometry, but these findings lack specificity 3

Critical Diagnostic Pitfalls to Avoid

• Never diagnose asthma based solely on symptoms or chest X-ray findings without objective lung function testing in children ≥5 years old 1, 4
• Do not use vague labels like "reactive airway disease" or "wheezy bronchitis" that delay proper diagnosis and treatment 1, 5
• Avoid relying on allergy testing to diagnose asthma—it has low specificity and should only be used to identify triggers after diagnosis is established 4
• Remember that normal spirometry does not exclude asthma, as lung function is frequently normal during stable disease; repeat testing when symptomatic is recommended 4