From the Guidelines
A FEV1/FVC ratio of 0.79 is considered normal, indicating no significant airflow obstruction in the lungs. This ratio represents the proportion of air that can be forcefully exhaled in the first second (FEV1) compared to the total forced vital capacity (FVC). According to the most recent guidelines, a normal FEV1/FVC ratio is typically above 0.70-0.75, so 0.79 falls within the normal range 1.
Clinical Implications
The significance of this ratio is that it helps distinguish between obstructive lung diseases (like asthma or COPD, which would show a reduced ratio) and restrictive lung diseases (which typically maintain a normal or elevated ratio). While this single value is normal, a complete pulmonary function test interpretation would also consider absolute FEV1 and FVC values, as well as other parameters and clinical context to provide a comprehensive assessment of lung function.
Management
No specific treatment or medication is needed for this finding alone. However, it is essential to consider the clinical context and other parameters, such as symptoms and exposure risk factors, to determine the overall management plan. The GOLD 2025 report recommends that the presence or absence of airflow obstruction should be confirmed by repeat spirometry on a separate occasion if the post-BD FEV/FVC ratio is between 0.60 and 0.80 1.
Key Points
- A FEV1/FVC ratio of 0.79 is considered normal.
- No significant airflow obstruction is indicated.
- No specific treatment or medication is needed for this finding alone.
- A complete pulmonary function test interpretation should consider absolute FEV1 and FVC values, as well as other parameters and clinical context.
- Repeat spirometry may be necessary to confirm the presence or absence of airflow obstruction in certain cases 1.
From the Research
Significance of FEV1/FVC Ratio
The FEV1/FVC ratio is a crucial metric in assessing lung function, particularly in the diagnosis of chronic obstructive pulmonary disease (COPD).
- A ratio of 0.79 is below the normal threshold of 0.80 or 0.90, depending on the reference value used 2.
- Studies have shown that an FEV1/FVC ratio below 0.90 is associated with an increased risk of all-cause mortality in the general population 3.
- Specifically, an FEV1/FVC ratio between 0.60 and 0.90 has been linked to a lower risk of all-cause mortality compared to a ratio of 0.90 or higher, after adjusting for confounding factors 3.
- In patients with limited-stage small cell lung cancer, an FEV1/FVC ratio of less than 0.74 has been found to be a potential prognostic factor for overall survival and progression-free survival 4.
Clinical Implications
The clinical significance of an FEV1/FVC ratio of 0.79 can be understood in the context of airflow obstruction and COPD diagnosis.
- Airflow obstruction is typically defined by an FEV1/FVC ratio below a fixed cutoff (usually <0.70) or the lower limit of normal (LLN) from reference equations 2, 5.
- The use of a fixed ratio alone may lead to misdiagnosis of COPD, and guidelines should consider requiring both a low FEV1/FVC ratio and a low FEV1 to establish a diagnosis 6.
- Risk stratification using the LLN of FEV1/FVC can help identify patients with COPD who are at risk for adverse postoperative outcomes after thoracic surgery 5.
Comparison with Other Ratios
It is essential to consider the FEV1/FVC ratio in conjunction with other clinical factors and patient-reported outcomes.