Spirometry and COPD screening: who is tested, and what the numbers mean

Is it a screening test?

• Adults without symptoms: the USPSTF recommends against screening for COPD (grade D, 2022, the same as in 2016). It applies to adults who do not notice or report breathing symptoms. (USPSTF, 2022)
• Why: it found no studies that directly show screening people without symptoms reduces illness or death or improves quality of life, and not enough evidence that treating COPD found this way does either. Questionnaires about risk factors and symptoms found 67% to 90% of people with COPD but also flagged many without it (specificity 25% to 73%). (USPSTF, 2022)
• Other groups: in 2011 the American College of Physicians, the American College of Chest Physicians, the American Thoracic Society and the European Respiratory Society also recommended against screening with spirometry in people without symptoms, and for using it to diagnose airflow obstruction in people with symptoms. (USPSTF, 2022)

Other lung tests with a D or I grade are on screening tests you may not need. The lung screening the USPSTF does recommend, a yearly low-dose CT for some people who smoke or used to, is on lung cancer screening.

Who is tested instead

• People with symptoms: the USPSTF recommendation does not apply to people with a chronic cough, sputum (phlegm), difficulty breathing or wheezing. (USPSTF, 2022) NICE says to suspect COPD in people over 35 who have a risk factor, usually smoking now or in the past, and breathlessness on exertion, a chronic cough, regular sputum, frequent winter "bronchitis" or wheeze. (NICE NG115)
• People at very high risk: the USPSTF recommendation also does not cover people with alpha-1 antitrypsin deficiency, an inherited condition that raises the risk of COPD, or workers exposed to certain toxins on the job. (USPSTF, 2022)
• Risk factors: cigarette smoking is the leading cause of COPD in the US. About 15% of people who smoke and 8% of people who used to smoke report a COPD diagnosis, compared with 3% of adults who never smoked. Secondhand smoke, traffic pollution, wood smoke and workplace fumes, dust and chemicals also contribute, as do a history of asthma or childhood chest infections. (USPSTF, 2022)

NHLBI suggests telling your provider about your smoking, secondhand smoke, air pollution, chemical fumes or dust, any family history of COPD, and how long you have had a cough or shortness of breath that gets worse over time. (NHLBI) The screenings that change with smoking history: screenings if you smoke.

What the test is like

• Before: MedlinePlus says not to eat a heavy meal and not to smoke for 4 to 6 hours before the test. (MedlinePlus) The NHS may ask you not to smoke for 24 hours, not to eat a large meal for at least 2 hours, not to drink alcohol for at least 4 hours, and to wear loose clothing. You will be told whether to stop any medicines; do not stop one on your own. (NHS)
• Checks first: your height and weight are measured, because they are needed to calculate your results. The test is not done if you have a chest infection, certain heart problems or uncontrolled high blood pressure, or have recently had a heart attack, stroke or some types of surgery. (NHS)
• During: you sit with a soft clip on your nose, take a deep breath until your lungs are full, seal your lips around a tube and blow out as hard and fast as you can until your lungs are empty. This is done 3 times in all. (NHS) A poor seal around the mouthpiece can make the results inaccurate. (MedlinePlus)
• A second round: you may be asked to breathe in a medicine that opens the airways and blow into the tube again, so the results before and after can be compared. (NHLBI) (NHS)
• How it feels: you may be briefly short of breath, lightheaded or dizzy, and you may cough. (MedlinePlus) (NHS)

FEV1, FVC and the ratio

Spirometry measures the flow and volume of air you breathe out. Diseases such as COPD and asthma mainly affect the airways and make the lungs take longer to empty; these are called obstructive lung disorders. (MedlinePlus) That is why a low FEV1/FVC ratio, a smaller share of the breath coming out in the first second, points to obstruction. (GOLD and GLI, 2026)

Two cutoffs for the ratio

• Fixed ratio (GOLD): a ratio below 0.70 measured after a medicine that opens the airways confirms airflow obstruction and COPD in people with symptoms and significant exposure to irritants. (USPSTF, 2022) GOLD keeps it because it is simple and does not depend on reference values. (GOLD and GLI, 2026)
• Lower limit of normal (ATS/ERS and GLI): the ratio is compared with the lowest 5% of healthy people of the same age, height and sex. (GOLD and GLI, 2026)
• Why it matters with age: the fixed ratio does not allow for changes in lung function with age, so it may flag fewer younger and more older people; the lower limit of normal flags more younger and fewer older people. A ratio of 0.65 at age 80 is above that age's lower limit (about 0.6) but below 0.70. (GOLD and GLI, 2026) NICE likewise advises considering other causes in older people with a ratio below 0.7 but no typical symptoms, and considering COPD in younger people with symptoms even when the ratio is above 0.7. (NICE NG115)
• Near the cutoff: GOLD and GLI say that where the two disagree, or more often where the ratio is between 0.6 and 0.8, the test should be repeated or followed by more tests. Spirometers can vary by up to 5% between repeated tests. (GOLD and GLI, 2026)

Percent predicted, and why it depends on age, height and sex

Your results are compared with predicted values for people like you in age, sex, height and weight, and given as a percentage of them. They are abnormal if they are significantly lower. Normal ranges can vary slightly between labs. (MedlinePlus) The lower limit of normal allows for the change in lung function with age, which reflects lung tissue losing elasticity, so the same result can be normal at one age and low at another. (GOLD and GLI, 2026) When the ratio is below 0.70, GOLD grades how severe the obstruction is by FEV1 percent predicted: (USPSTF, 2022)

Severity can also be graded by symptoms and past flare-ups, not only by the numbers. (USPSTF, 2022) GOLD and GLI agree that older race-based reference values could underestimate how severe obstruction is, and GOLD considers the race-neutral GLI equations published in 2022 the most appropriate for now. (GOLD and GLI, 2026) More on race in screening: screening and race or ethnicity.

Where they differ:

• Ratio cutoff: GOLD uses a fixed 0.70; the ATS/ERS interpretation standards and GLI use the lower limit of normal. GOLD and GLI say only a small share of people are classified differently and that both are useful in people with symptoms and exposure. (GOLD and GLI, 2026)
• Severity: GOLD grades by FEV1 percent predicted; ATS/ERS use z-scores, which measure how far a result is from the average for age, height and sex. (GOLD and GLI, 2026)
• Before or after the airway medicine: NICE measures after it to confirm COPD, (NICE NG115) and the USPSTF definition is also based on it. (USPSTF, 2022) GOLD and GLI note that results before it are also reproducible and that obstruction found only afterward is uncommon. (GOLD and GLI, 2026)
• Before symptoms: NHLBI notes that spirometry can detect COPD before symptoms are recognized, (NHLBI) but the USPSTF found no evidence that screening people without symptoms improves health. (USPSTF, 2022) In England, the NHS says you may be offered spirometry if you are over 55 and smoke, as part of lung cancer screening. (NHS)
• Not smoking before the test: 4 to 6 hours (MedlinePlus) or 24 hours (NHS). (MedlinePlus) (NHS) Follow the instructions from the place doing your test.

After the test

Abnormal results usually mean you may have a chest or lung disease. Obstructive diseases make the lungs hold too much air; other conditions, such as scarring of the lungs or muscle weakness, make them hold too little, which is a different pattern. (MedlinePlus) GOLD and GLI agree that spirometry alone is not enough to diagnose COPD, (GOLD and GLI, 2026) and the ERS/ATS standard says results must be read with clinical expertise and with the natural variability of the test in mind. (ERS/ATS, 2022) If COPD is diagnosed, NHLBI suggests asking about screening for alpha-1 antitrypsin deficiency, especially if relatives have it or were diagnosed with COPD in their 40s or 50s. (NHLBI) Your doctor decides what your result means for you.

This page does not give inhaler, medicine or treatment advice. If you have a flagged result, see after an abnormal screening result for questions to ask.

Questions people ask

Should I have spirometry if I have no breathing symptoms?

The USPSTF recommends against screening adults without respiratory symptoms for COPD (grade D). It found no studies showing that screening people without symptoms improves health, and not enough evidence that treating COPD found this way helps. This does not apply if you have symptoms such as a long-lasting cough, phlegm, trouble breathing or wheezing. (USPSTF, 2022)

What is a normal FEV1/FVC ratio?

There are two ways to judge it. GOLD uses a fixed cutoff: a ratio below 0.70 after a medicine that opens the airways, in someone with symptoms and exposure, confirms airflow obstruction. ATS/ERS and the Global Lung Function Initiative (GLI) use the lower limit of normal, the lowest 5% of healthy people of the same age, height and sex. At 80, for example, that limit is about 0.6. (USPSTF, 2022) (GOLD and GLI, 2026)

What does FEV1 percent predicted mean?

It compares your FEV1 with the value expected for people of your age, sex, height and weight. GOLD uses it to grade how severe obstruction is: 80% or more is mild, 50% to under 80% moderate, 30% to under 50% severe and under 30% very severe. (MedlinePlus) (USPSTF, 2022)

Does a low ratio mean I have COPD?

Not by itself. GOLD and GLI agree that spirometry alone is not enough to diagnose COPD and that no one should be labeled with it from a lung test result without a clinical history. Results near the cutoffs are often repeated or followed by more tests. (GOLD and GLI, 2026)

How long does a spirometry test take, and does it hurt?

The NHS says the appointment should take no more than an hour. The forced breathing can leave you briefly short of breath, lightheaded or dizzy, and you may cough. (NHS) (MedlinePlus)

Related

• Screenings if you smoke
• Lung cancer screening
• Low-dose CT lung scan: what to expect
• Screening tests you may not need
• Sleep apnea screening
• Annual physical tests by age