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 reduced ratio below 0.70 indicating airflow obstruction, and spirometry measurements should be performed after adequate bronchodilator administration to establish the diagnosis, as recommended by the GOLD Science Committee in 2025 1. The FEV1/FVC ratio represents the proportion of a person's vital capacity that they can expire in the first second of forced expiration. In healthy adults, this ratio is typically between 0.70-0.80, but in COPD patients, airflow obstruction causes this value to fall below 0.70 even after bronchodilator administration. Key points to consider:

• The severity of COPD is primarily classified based on the FEV1 percentage of predicted value, ranging from mild (FEV1 ≥ 80% predicted) to very severe (FEV1 < 30% predicted) 1.
• This reduced ratio occurs because COPD causes airway narrowing, loss of elastic recoil, and air trapping, which particularly affects expiratory flow rates 1.
• As COPD progresses, the FEV1 typically declines faster than the FVC, causing the ratio to decrease further over time 1.
• The GOLD Science Committee recommends using pre-BD spirometry to rule out COPD and post-BD measurements to confirm the diagnosis, which will reduce clinical workload and limit COPD overdiagnosis 1.
• Post-BD results close to the threshold should be repeated to ensure a correct diagnosis is made, and post-BD measurements ensure that volume responders are not overlooked 1.

From the FDA Drug Label

In these trials, 3136 and 1232 COPD patients were exposed to roflumilast 500 mcg once daily for 6 months and 1 year, respectively. The population had a median age of 64 years (range 40 to 91), 73% were male, 92.9% were Caucasian, and had COPD with a mean pre-bronchodilator forced expiratory volume in one second (FEV 1) of 8.9 to 89.1% predicted.

The significance of the Forced Expiratory Volume in 1 second (FEV1) to Forced Vital Capacity (FVC) ratio in Chronic Obstructive Pulmonary Disease (COPD) is not directly addressed in the provided drug labels 2 and 3. However, the labels do mention FEV1 as a measure of pulmonary function in patients with COPD.

• FEV1 is used to assess the effectiveness of treatments, such as ipratropium bromide and roflumilast, in improving lung function in patients with COPD.
• The FEV1/FVC ratio is a key metric in diagnosing and managing COPD, as it helps to assess the severity of airway obstruction.
• A lower FEV1/FVC ratio indicates more severe airway obstruction, which is a hallmark of COPD. The provided drug labels do not explicitly discuss the significance of the FEV1/FVC ratio in COPD, but it is a crucial measure in clinical practice for assessing disease severity and monitoring treatment response.

From the Research

Significance of FEV1/FVC Ratio in COPD

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

Diagnostic Criteria

The diagnosis of COPD relies on the presence of chronic airflow limitation, defined by an FEV1/FVC ratio less than 70% [(5,6)]. The use of a fixed ratio of 0.7 or less may lead to misdiagnosis of COPD, and guidelines should be reconsidered to require both spirometry abnormalities to reduce overdiagnosis 7.

Clinical Relevance

Patients with airflow limitation based on both a low FEV1/FVC ratio and a low FEV1 have stronger associations with clinical outcomes, including respiratory symptoms, disability, health status, exacerbations, and cardiovascular disease 7. The measurement of pulmonary volumes, including spirometry, is required for the diagnosis and follow-up of COPD patients 6.

Comparison of FVC and VC

The use of forced vital capacity (FVC) as a proxy for vital capacity (VC) may result in underdiagnosis of mild COPD 8. The prevalence of COPD is significantly higher when the ratio FEV1/VC is calculated using the highest value of slow vital capacity (SVC) or FVC compared with using FVC only 8.

Key Points

• A postbronchodilator FEV1/FVC ratio of 0.7 or less is diagnostic of COPD 4.
• The diagnosis of COPD relies on the presence of chronic airflow limitation, defined by an FEV1/FVC ratio less than 70% [(5,6)].
• Patients with airflow limitation based on both a low FEV1/FVC ratio and a low FEV1 have stronger associations with clinical outcomes 7.
• The use of FVC as a proxy for VC may result in underdiagnosis of mild COPD 8.