Asthma Diagnosis Guidelines

Introduction to Asthma Diagnosis

A positive test for asthma requires objective evidence of variable airflow limitation, with the gold standard being a bronchodilator reversibility test showing an increase in FEV1 of ≥12% and ≥200mL from baseline after administration of a bronchodilator, as recommended by the European Respiratory Society 1
Variable airflow limitation is the hallmark of asthma, according to the European Respiratory Society guidelines 1
No single test can definitively diagnose asthma in all cases; multiple tests may be required, as stated by the European Respiratory Society 1 and the European Respiratory Review 5

The European Respiratory Society recommends at least two objective test results be abnormal to confirm asthma diagnosis, with a focus on spirometry with bronchodilator reversibility testing and FeNO measurement as first-line tests 1
Bronchodilator reversibility testing has high specificity (90-98%) but lower sensitivity (35-36%) for asthma diagnosis, as reported by the European Respiratory Journal 1
A positive result for bronchodilator reversibility testing is defined as an increase in FEV1 of ≥12% and ≥200mL from baseline after bronchodilator administration, according to the European Respiratory Journal 1
Methacholine challenge testing has high sensitivity but lower specificity than bronchodilator testing, and is most useful when pretest probability of asthma is 30-70%, as stated by the American Journal of Respiratory and Critical Care Medicine 3
Exercise challenge testing is particularly useful for diagnosing exercise-induced asthma, with a positive result defined as a fall in FEV1 >10% from baseline after standardized exercise, as recommended by the European Respiratory Society 1
FeNO measurement is a useful diagnostic tool, with a positive result defined as a FeNO value ≥25 ppb in a child with asthma symptoms, indicating eosinophilic airway inflammation and supporting diagnosis of asthma when combined with clinical symptoms, as reported by the European Respiratory Journal 1 and the European Respiratory Review 5

A negative bronchodilator test does not rule out asthma due to its low sensitivity, as stated by the European Respiratory Journal 1
Methacholine challenge testing has limited utility in patients with baseline airway obstruction, as reported by the American Journal of Respiratory and Critical Care Medicine 3
Relying solely on symptoms without objective testing leads to misdiagnosis, with studies showing 33.1% of patients with physician-diagnosed asthma having no evidence of asthma on pulmonary function tests, as reported by the European Respiratory Review 5

First-line tests for asthma diagnosis include spirometry with bronchodilator reversibility testing and FeNO measurement, as recommended by the European Respiratory Society 1
If spirometry is abnormal, perform bronchodilator reversibility testing, and if positive, asthma is confirmed, as stated by the European Respiratory Society 1
If spirometry is normal but symptoms persist, measure FeNO, consider PEF variability testing, and consider bronchial challenge testing (methacholine or exercise), as recommended by the European Respiratory Society 1
For exercise-related symptoms, an exercise challenge test showing >10% fall in FEV1 confirms exercise-induced asthma, as reported by the European Respiratory Journal 1