Asthma diagnosis FEV1/FVC
What is the FEV1/FVC ratio for asthma diagnosis? When I did a spirometry course at the AAAAI meeting a few years ago, I was informed that FEV1/FVC ratio of < 0.80. Is this correct?
Obstruction of airflow is defined by a reduced FEV1 (forced exhalation volume in one second) to FVC (forced vital capacity). This is a result in a relatively greater decrease in FEV1 compared to FVC, whereas in restrictive disease these 2 parameters decrease proportionally and the FEV1/FVC ratio does not change. Since FEV1 is decreased more in obstructive disease, FEV1 will generally show the greater change with treatment, such as an acute bronchodilator. The criteria for reversibility is 12% change in FEV1 and at least 200 ml.
FVC reversibility does occur in airflow obstruction and there has been interest in utilizing the change in FVC for clinical assessment of obstruction (1,2). The American Thoracic Society and the European Respiratory Society established a common interpretative strategy for lung function testing with 12% increase in either FEV1 or FVC and a 200 ml increase in FEV1 or FVC as reversibility criteria (3). In some studies the response in FVC is much greater than FEV1, but this is primarily in severe COPD with hyperinflation (4) this work has been in COPD rather than asthma.
I shared your question with Tom Casale, MD, an internationally known expert in asthma. His response was to provide the criteria of reversibility from the Global Initiative for Asthma (GINA).
In summary, reversibility of airflow obstruction in asthma is defined by an increase in FEV1 of 12% or 200 ml. There is generally an increase in FEV1/FVC since FVC changes less than FEV1, making FVC a less useful parameter for assessing reversibility. Some patients, particularly with severe COPD, may show a greater response of FVC than FEV1.
1. Girard WM, Light RW. Should the FVC be considered in evaluating response to bronchodilator. Chest 1983;84:87-89.
2. Saad, Helmi Ben, et al. "The forgotten message from gold: FVC is a primary clinical outcome measure of bronchodilator reversibility in COPD." Pulmonary pharmacology & therapeutics 21.5 (2008): 767-773.
3. Pellagrino R, Viegi G, et al. Interpretative strategies for lung function tests. Eur Respir J 2005;26:948-968.
4. Newton MF, O’Donnell DE, Forkert L. Response of lung volumes to inhaled salbutamol in a large population of patients with severe hyperinflation. Chest 2002;121:1042-50.
We hope this information is of help to you and your practice.
All our best.
Dennis K. Ledford, MD, FAAAAI
Tom B. Casale, MD, FAAAAI