Yes, this is asthma
Your 15-year-old patient meets diagnostic criteria for asthma based on spirometry showing reversible small airway obstruction, regardless of negative allergy testing. 1, 2
Why This Is Asthma
The European Respiratory Society guidelines for children aged 5-16 years establish that asthma diagnosis requires at least two abnormal objective test results from first-line testing (spirometry, bronchodilator reversibility, or FeNO). 2 Your patient has:
- Characteristic symptoms: Recurrent bronchoconstriction and dyspnea ("not being able to take a full breath") 1
- Objective airflow obstruction: Small airway obstruction on spirometry 2
- Reversibility: Positive bronchodilator test demonstrating reversible airflow obstruction 1, 2
This combination of abnormal spirometry plus positive bronchodilator reversibility fulfills the diagnostic criteria. 2
Why Negative Allergy Testing Doesn't Matter
Allergy testing should NOT be used to diagnose asthma. 1, 3 The European Respiratory Society explicitly states that allergy tests may help identify triggers but have low specificity for asthma diagnosis. 3 Asthma encompasses both atopic and non-atopic phenotypes, and your patient likely has non-atopic asthma. 4, 5
Normal total IgE and negative skin prick tests simply indicate she doesn't have allergic sensitization driving her disease—this is a recognized asthma phenotype. 4, 5
Small Airway Obstruction Is Clinically Significant
Small airway tests (FEF25-75, FEF50, FEF75) are more sensitive than large airway tests (FEV1, PEFR) for detecting obstruction in childhood asthma. 6 In mild obstruction, FEV1 detects only 6.8% of abnormal tests while FEF75 detects 33%. 6 Your patient's small airway findings are diagnostically meaningful and should not be dismissed. 6
Critical Pitfall to Avoid
Do not rely on an empiric treatment trial where symptom improvement alone confirms diagnosis—the European Respiratory Society explicitly recommends against this approach as it leads to misdiagnosis. 7, 3, 2 You already have objective confirmation, so proceed directly to treatment.
Next Steps
- Initiate controller therapy with inhaled corticosteroids as first-line treatment 3
- Consider measuring FeNO (≥25 ppb supports eosinophilic inflammation and may predict treatment response) 7, 2, 8
- Check eosinophil count (≥300/μL increases exacerbation risk) 8
- Repeat spirometry every 1-2 years to monitor disease progression 7
- Document triggers (exercise, viral infections, irritants) to guide avoidance strategies 7, 2