Introduction: The level of change in lung function to define a clinically meaningful reversibility test is the source of much debate.

Aim: To improve understanding of the sensitivity of bronchodilator thresholds in children and adults with severe asthma.    

Methods: Data from reversibility assessments (2.5 mg nebulised salbutamol) were retrospectively analysed from patients with confirmed severe asthma. The sensitivity of reversibility testing was assessed against 6 commonly used criteria. Changes in forced expired volume in one second (FEV₁) after bronchodilation were assessed and presented as median and IQR. Differences between children and adults were assessed with Chi-squared or Fisher?s exact test, with significance accepted at an ?-level of p<0.05. Reference values for FEV₁ were calculate using current Global Lung Initiative reference equations.

Results: Median improvement in FEV₁ was 290 mL (160-497) for adults and 150 mL (40-340) for children. In those with a positive bronchodilator response (200 mL and 12%), 86.4% (223 of 258) had obstructive spirometry at baseline.

Conclusions: 8% and 10% change from predicted criteria are most sensitive to asthma in children. In adults, a lower threshold of ?160 mL change in FEV₁ offers much higher sensitivity; however, the implications for diagnostic specificity are unclear.   

References

1.      Stanojevic et al, 2022, ERS technical standard on interpretation of lung function tests, ERJ.