What is the minimum amount of improvement in Forced Expiratory Volume in 1 second (FEV1) necessary to demonstrate reversibility in a patient with suspected asthma following administration of a bronchodilator, such as albuterol (short-acting beta-agonist, SABA)?

From the Guidelines

The minimum improvement in FEV1 required to demonstrate bronchodilator reversibility in suspected asthma is an increase of at least 12% and 200 mL from baseline after administration of a bronchodilator. This is based on the most recent and highest quality study available, which suggests that an improvement of greater than or equal to 12% and 200 ml in patients with asthma with baseline airway obstruction is usually considered to be significant 1. The standard protocol involves administering 4 puffs (400 mcg) of albuterol via metered-dose inhaler with a spacer or 2.5 mg via nebulizer, then repeating spirometry after 15 minutes. Both criteria must be met - both the percentage increase and the absolute volume increase - as smaller changes may represent normal variability rather than true reversibility.

Key Considerations

• The reversibility criterion is important for distinguishing asthma from other obstructive lung diseases like COPD, which typically shows less reversibility to bronchodilators.
• In some patients, especially those with more severe obstruction or longer-standing asthma, reversibility may not be evident in a single test and might require repeated testing or a trial of oral corticosteroids (such as prednisone 40 mg daily for 5-7 days) to demonstrate improvement.
• The use of a fixed FEV1/FVC ratio as a cut-point should be done with caution, as it results in false-positive diagnoses of obstruction in older adults and potentially false-negative diagnoses of obstruction in younger adults, given a natural decline in FEV1 with age 1.

Clinical Implications

• Spirometry is a fundamental measure of asthma control and provides an objective and highly reproducible measure of airflow limitation caused by smooth muscle contraction or structural changes.
• The analysis of spirometric data from serial visits may incorporate mixed model analyses, or calculation of FEV1 area-under-the-curve to take advantage of multiple datapoints 1.
• Reference values for percent predicted FEV1 and/or FVC are primarily used for inclusion or exclusion criteria for clinical trials, and to characterize the study population 1.

From the FDA Drug Label

Clinically significant improvement in pulmonary function (defined as maintenance of a 15% or more increase in FEV1 over baseline values)

The minimum amount of improvement in FEV1 necessary to demonstrate reversibility is 15% or more over baseline values 2.

• This increase in FEV1 indicates a significant response to the bronchodilator, such as albuterol.
• An increase of less than 15% may not be considered clinically significant.

From the Research

Minimum Improvement in FEV1 for Reversibility

• The minimum amount of improvement in Forced Expiratory Volume in 1 second (FEV1) necessary to demonstrate reversibility in a patient with suspected asthma following administration of a bronchodilator is defined by international guidelines as an absolute and percentage change from baseline in FEV1 ≥12% and 200 mL 3.
• This definition is based on the American Thoracic Society (ATS) and European Respiratory Society (ERS) criteria.
• However, some studies suggest that a less stringent improvement in FEV1 might be applicable in children and adolescents, and that changes in other lung function parameters, such as peak expiratory flow (PEF) and forced expiratory flow (FEF25-75%), may also be useful in assessing reversibility 4.

Alternative Criteria for Reversibility

• Alternative functional criteria to assess airflow-limitation reversibility in asthma include changes in PEF, FEF25-75%, residual volume (RV), inspiratory capacity (IC), airway resistance (Raw), and specific airway conductance (sGaw) 3.
• The most accurate predictors of a significant bronchodilator response were found to be the absolute and percentage improvements in PEF (≥0.4 L/s and 8%), FEF25-75% (≥0.087 L/s and 27%), and the percentage of sGaw compared with that at baseline (≥25%) 3.

Clinical Implications

• The choice of criteria for reversibility may impact the diagnosis and management of asthma, particularly in children and adolescents 4.
• Long-acting beta2-adrenergic agonists (LABAs) and inhaled corticosteroids are commonly used in combination for the management of persistent asthma, and the role of LABAs in asthma management is supported by updated asthma guidelines 5.