What is the significance of Forced Expiratory Volume in 1 second (FEV1) to Forced Vital Capacity (FVC) ratio in Chronic Obstructive Pulmonary Disease (COPD)?

From the Guidelines

The FEV1/FVC ratio is a crucial diagnostic criterion for COPD, with a threshold of <0.7 indicating airflow obstruction, as recommended by the GOLD Science Committee in 2025 1. This ratio represents the proportion of a person's vital capacity that they can expire in the first second of forced expiration. In COPD, airflow obstruction causes air to become trapped in the lungs, making it difficult to exhale quickly. As the disease progresses, the FEV1 (forced expiratory volume in one second) decreases more rapidly than the FVC (forced vital capacity), leading to a lower ratio. The severity of COPD is primarily classified based on the FEV1 percentage of predicted value, with GOLD stages ranging from 1 (mild, FEV1 ≥ 80% predicted) to 4 (very severe, FEV1 < 30% predicted), all requiring the FEV1/FVC ratio to be below 0.70, as supported by recent evidence 1. Some key points to consider when interpreting the FEV1/FVC ratio in COPD diagnosis include:

• The use of pre- and post-bronchodilator spirometry to diagnose COPD, with post-bronchodilator measurements ensuring that volume responders are not overlooked and limiting COPD overdiagnosis 1.
• The importance of considering the clinical evaluation and spirometry results together to reduce the potential for COPD overdiagnosis and overtreatment 1.
• The need for widespread use of spirometry in clinical practice, despite practical implementation and training issues contributing to low uptake 1. The reduced FEV1/FVC ratio reflects the pathophysiological changes in COPD, including loss of elastic recoil in the lungs, airway inflammation, mucus hypersecretion, and airway narrowing, which collectively impair airflow, particularly during expiration, as described in earlier studies 1.

From the FDA Drug Label

The diagnosis of COPD was based upon a prior clinical diagnosis of COPD, a smoking history (at least 10 pack-years), age (at least 40 years), and spirometry results (pre-bronchodilator baseline FEV1 at least 30% and less than 70% of the predicted value, and the FEV1/FVC less than 70%)

The FEV1/FVC ratio is significant in Chronic Obstructive Pulmonary Disease (COPD) as it is used to diagnose the condition. A ratio of less than 70% indicates the presence of COPD. This ratio is calculated by dividing the Forced Expiratory Volume in 1 second (FEV1) by the Forced Vital Capacity (FVC). In the context of COPD, a lower FEV1/FVC ratio suggests airflow limitation, which is a hallmark of the disease 2.

• Key points:
  • FEV1/FVC ratio is used to diagnose COPD
  • A ratio of less than 70% indicates COPD
  • This ratio is calculated by dividing FEV1 by FVC
  • A lower FEV1/FVC ratio suggests airflow limitation, a hallmark of COPD

From the Research

Significance of FEV1/FVC Ratio in COPD

The FEV1/FVC ratio is a crucial metric in the diagnosis and management of Chronic Obstructive Pulmonary Disease (COPD) 3, 4, 5, 6, 7.

• A postbronchodilator FEV1/FVC ratio of 0.7 or less is diagnostic of COPD in patients with symptoms such as dyspnea, chronic cough, or sputum production, and a history of irritant exposure 3.
• The FEV1/FVC ratio is used to classify the severity of airflow obstruction in COPD, with lower ratios indicating more severe disease 5.
• The ratio can be used to identify patients who may benefit from specific treatments, such as long-acting beta2-agonists and long-acting muscarinic antagonists 3.

Comparison with Other Diagnostic Criteria

• The FEV1/FVC ratio has been compared to other diagnostic criteria, such as the FEV1/FEV6 ratio, and has been found to be a reliable and robust measure of airflow obstruction 4.
• The use of a fixed ratio versus the lower limit of normal for FEV1/FVC has been debated, with some studies suggesting that the fixed ratio may lead to misdiagnosis of COPD 6.
• Bronchodilator reversibility testing may not be necessary in the diagnostic screening algorithm for early COPD case finding, as it may result in underdiagnosis of COPD 7.

Clinical Relevance

• The FEV1/FVC ratio is associated with clinical outcomes, such as respiratory symptoms, disability, health status, exacerbations, and cardiovascular disease 6.
• A low FEV1/FVC ratio is strongly associated with adverse outcomes, particularly when combined with a low FEV1 6.
• The ratio can be used to identify patients who may benefit from pulmonary rehabilitation and supplemental oxygen therapy 3.