What is the recommended approach to diagnose asthma in a pediatric patient with respiratory symptoms?

Diagnosing Asthma in Children Aged 5-16 Years

Do not diagnose asthma in children based on clinical history alone or following a single abnormal objective test; instead, use a combination of at least two abnormal objective tests including spirometry, bronchodilator reversibility testing, and fractional exhaled nitric oxide (FeNO) as first-line diagnostic tools. 1, 2

Why Objective Testing is Essential

Diagnosing asthma based solely on symptoms and clinical examination results in substantial misdiagnosis rates in children, leading to both over-diagnosis with unnecessary corticosteroid exposure and under-diagnosis with preventable morbidity. 1 The European Respiratory Society developed evidence-based guidelines specifically for children aged 5-16 years because extrapolating from adult data is inappropriate—children require different test cut-offs and diagnostic approaches. 1

First-Line Diagnostic Tests

Spirometry

• Perform spirometry to measure FEV1 and FEV1/FVC ratio, with abnormal results defined as values less than the lower limit of normal (LLN) and/or <80% predicted. 2
• Critical caveat: Normal spirometry does not exclude asthma, as children may be asymptomatic at the time of testing. 2
• Abnormal spirometry alone does not confirm asthma—it requires additional supporting evidence. 1, 2

Bronchodilator Reversibility (BDR) Testing

• Perform BDR testing even when spirometry is normal if clinical suspicion remains high. 2
• A positive BDR test indicates reversible airflow obstruction characteristic of asthma. 2
• This test should be conducted as part of the initial diagnostic workup, not as a standalone test. 1

Fractional Exhaled Nitric Oxide (FeNO)

• Measure FeNO before performing spirometry, using a cut-off of ≥25 ppb. 2
• Elevated FeNO suggests eosinophilic airway inflammation, supporting an asthma diagnosis. 2
• FeNO has high diagnostic accuracy (AUC 0.80) and contributes significantly to diagnosis in school-aged children. 3

Diagnostic Algorithm

Step 1: Clinical Assessment

• Document specific symptom patterns, particularly wheeze (sensitivity 55-86%, specificity 64-90%), which is the most diagnostically useful symptom. 2
• Ask about frequency: more than three wheezing attacks per year has high specificity (90%). 3
• Identify specific triggers: wheeze triggered by pollen (specificity 83%) or pets (specificity 99%). 3
• Do not rely on cough or breathing difficulty alone—these are nonspecific symptoms that should not be used to diagnose asthma. 1, 2

Step 2: Perform All Three First-Line Tests

• Conduct FeNO measurement (before spirometry). 2
• Perform spirometry with bronchodilator reversibility testing. 1, 2
• All three tests should be completed during the initial evaluation. 1

Step 3: Interpret Results

• Confirm asthma diagnosis when at least two objective tests are abnormal (e.g., abnormal spirometry + positive BDR, or elevated FeNO + positive BDR). 2, 4
• If only one test is abnormal, do not make the diagnosis—consider additional testing. 1

Step 4: When Initial Tests Are Normal But Suspicion Remains High

• Consider 2-week peak expiratory flow rate (PEFR) variability monitoring with twice-daily measurements; variability >12% suggests asthma. 2
• Consider bronchial challenge testing (methacholine or exercise challenge, which have AUC of 0.81 and 0.74 respectively). 3
• Repeat testing when the child is symptomatic, as asthma is a dynamic condition with variable test results over time. 2, 5

Critical Pitfalls to Avoid

Do Not Diagnose Based on Treatment Response Alone

• Never diagnose asthma based solely on improvement after a trial of preventer medication (inhaled corticosteroids or leukotriene receptor antagonists). 1, 2
• The European Respiratory Society found no evidence supporting this approach and recommends against it. 1
• A treatment trial can only be considered in symptomatic children with abnormal spirometry and negative BDR, and objective tests must be repeated after 4-8 weeks. 1

Do Not Rely on Single Test Results

• A single abnormal objective test is insufficient for diagnosis and leads to misdiagnosis. 1
• Conversely, a single normal test does not exclude asthma if clinical suspicion is high. 2

Consider Alternative Diagnoses

• In children with failure to thrive and steatorrhea, consider cystic fibrosis rather than escalating asthma therapy. 6
• Systematically exclude foreign body aspiration, cystic fibrosis, and other structural abnormalities. 4

Age-Specific Considerations

These evidence-based recommendations specifically apply to children aged 5-16 years who can reliably perform spirometry and other objective tests. 1, 2 For preschool-aged children unable to perform objective testing, diagnosis remains primarily clinical, though this represents a significant gap in diagnostic certainty. 7