Introduction:

Bronchodilator responsiveness (BDR) is a key diagnostic criterion for asthma. Many patients with strong clinical suspicion of asthma have negative BDR or are unable to stop inhaled medications before testing. GINA defines BDR as >12% and >200 mL increase in FEV₁ or FVC, while ATS/ERS suggests a >10% change in either.

Objective:

To compare BDR positivity rates based on GINA and ATS/ERS thresholds in patients with severe asthma on biologics and evaluate alternative diagnostic tools used when BDR is negative or not feasible.

Methods:

1. Population: 108 patients with severe asthma on biologics
2. BDR Testing: Completed in 95 patients
   1. 8 unable to withhold meds
   2. 1 failed testing
   3. 4 had no prior BDR attempt
3. Other Tools Used:
   1. Visit-to-visit FEV₁ variability
   2. Home PEF variability
   3. Bronchial challenge test
   4. Specialist multidisciplinary diagnosis

Results:

1. Among 63 patients with negative or no BDR:
   1. FEV₁ variability >10% between visits: 40 patients (63%)
   2. PEF variability >10%: 35 patients (56%)
   3. Positive bronchial challenge test: 2 patients
   4. Diagnosed via specialist review: 11 patients
2. PEF Variability:
   1. Assessed more frequently in patients with negative BDR
   2. Present in 38% of BDR-positive patients

Conclusion:

BDR positivity was observed in fewer than half of patients, regardless of the threshold used. This underscores its limited sensitivity in diagnosing severe asthma. PEF variability was a common and valuable diagnostic tool, often used when BDR was negative or unfeasible. PEF is cost-effective, widely accessible, and should be considered in asthma diagnosis, especially in low-resource settings.

Am J Respir Crit Care Med 2025; 211: A3072

American Thoracic Society 2025 International Conference, May 18-21, San Francisco