From the Guidelines
Spirometry is the primary breathing test ordered for diagnosing Chronic Obstructive Pulmonary Disease (COPD), specifically measuring forced expiratory volume in one second (FEV1) and forced vital capacity (FVC), with a ratio of FEV1/FVC less than 0.7 after bronchodilator administration confirming airflow obstruction consistent with COPD. This test is essential for diagnosing COPD as it provides an objective measurement of airflow limitation, which is necessary for confirming the presence of the disease 1. The use of pre- and post-bronchodilator spirometry is recommended, with the post-bronchodilator FEV1/FVC ratio being the most important measurement for diagnosing COPD 1.
Some key points to consider when interpreting spirometry results include:
- A post-bronchodilator FEV1/FVC ratio of less than 0.7 confirms the presence of airflow limitation consistent with COPD 1.
- The use of a fixed ratio of 0.7 may result in more frequent diagnosis of COPD in the elderly and less frequent diagnosis in young adults 1.
- Repeat spirometry may be necessary to confirm the diagnosis, especially if the initial post-bronchodilator FEV1/FVC ratio is between 0.6 and 0.8 1.
Additional pulmonary function tests, such as lung volume measurements, diffusion capacity testing, and bronchodilator reversibility testing, may also be ordered to assess the severity of obstruction and differentiate COPD from asthma 1. Arterial blood gas analysis may also be ordered to evaluate oxygen and carbon dioxide levels, especially in advanced disease 1.
Overall, spirometry is a crucial test for diagnosing COPD, and its results should be interpreted in the context of the patient's symptoms, medical history, and other diagnostic tests. The GOLD 2025 report 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.
From the Research
Breathing Tests for Diagnosing COPD
The primary breathing test used for diagnosing Chronic Obstructive Pulmonary Disease (COPD) is spirometry. This test measures the amount of air a person can breathe out and how quickly they can do it 2, 3, 4.
Spirometry Measurements
Spirometry detects persistent airflow limitation by measuring the ratio of forced expiratory volume in one second (FEV1) to forced vital capacity (FVC), with a post-bronchodilator FEV1/FVC ratio of less than 0.7 indicating COPD 2, 5, 4. Other measurements, such as FEV1/FEV6 and the slope of the expiratory flow-volume curve, have also been evaluated as potential diagnostic tools 3.
Importance of Spirometry in COPD Diagnosis
Spirometry is a safe and practical procedure that allows for the early detection of COPD, enabling prompt addressing of risk factors and optimization of treatment 4. However, despite its importance, spirometry is often underused in primary care, leading to substantial underdiagnosis of COPD 4, 6.
Key Points
- Spirometry is the primary breathing test used for diagnosing COPD 2, 3, 4.
- The post-bronchodilator FEV1/FVC ratio is used to detect persistent airflow limitation 2, 5, 4.
- Other spirometry measurements, such as FEV1/FEV6, may also be useful in diagnosing COPD 3.
- Spirometry is underused in primary care, leading to underdiagnosis of COPD 4, 6.