Importance of Pulmonary Function Tests in Asthma Diagnosis

Asthma affects nearly 34.3 million people in India, as reported by the Global Burden of Disease. While symptoms such as coughing, wheezing, and shortness of breath are common, they can also be linked to other lung problems. This is why Pulmonary Function Tests (PFTs) are used during diagnosis. These tests check how well the lungs work by measuring airflow, lung volume, and how easily air moves in and out. In this article, we discuss in detail what is PFT tests, their normal range, and how to interpret the results.

What is a Pulmonary Function Test?

Pulmonary function refers to the lungs’ ability to take in oxygen, expel carbon dioxide, and facilitate proper gas exchange with the bloodstream. PFT tests are a group of tests designed to evaluate this function using objective data. Unlike a basic questionnaire or physical exam, PFTs offer precise insights into lung health. One of the most commonly used methods spirometry can confirm whether airway narrowing is reversible, which is a classic feature of asthma.

Also read about Lung Cancer

What are the Different Types of Pulmonary Function Tests?

There are a few types of PFT tests that doctors use to diagnose asthma.

1. Spirometry – This is the most common test for checking lung function in asthma. In this test, the person is asked to take a deep breath and blow out as hard as possible into a machine called a spirometer. The machine records the amount of air pushed out and how quickly it comes out. Two important values from this test are FEV1 and FVC. If the FEV1 is low, it may mean that the person has asthma. This test can also be done after giving asthma medicine to check how well the lungs respond.
2. Peak Expiratory Flow or PEF Monitoring – This is a simple test that can even be done at home. It uses a small handheld tool called a peak flow meter. The person blows into it, and the tool shows how fast the air comes out of the lungs. The result is noted in litres per minute. Asthma often causes changes in breathing, so doctors look at how much the results go up and down during the day. If the numbers change a lot, it may mean the airways are narrowing and the person could have asthma.
3. Other Tests – Some other tests may be used in hospitals or special centres. These include the exhaled nitric oxide test, which checks for swelling in the airways, or a test that uses a medicine called methacholine to see how sensitive the airways are. These are done when the basic tests are not enough. But in most cases, spirometry and PEF are enough to confirm asthma.

When Should Someone Take a Pulmonary Function Test?

Doctors usually suggest a PFT if a person has breathing problems that do not go away or come back again and again. It may also be done to check how well asthma treatment is working. Even if the person feels fine, the test can show if the lungs are getting better or worse.

What is the PFT Test Normal Range?

PFTs may be normal in controlled or mild asthma. Here is a chart indicating pulmonary function test normal values by age –

How to Interpret Basic Asthma PFT Results?

When checking for asthma, doctors look for a few signs in the test results-

1. Airway Blockage – If the FEV1 to FVC ratio is lower than normal, it shows that the airways are blocked. This is common in asthma.
2. Change After Medicine – After giving asthma medicine, if the FEV1 goes up by more than 12 percent and at least 200 millilitres, it shows that the airway blockage can be treated, which confirms asthma.
3. Daily Changes in Peak Flow – If the highest and lowest peak flow readings in a day differ by more than 10 percent, it may point to asthma. Doctors often check these readings over one to two weeks.

Pulmonary function tests are an important part of diagnosing and managing asthma. They help doctors see how well the lungs are working and how the person is responding to treatment. If anyone is experiencing asthma-like symptoms, they should consult with their doctor immediately and undergo appropriate tests. To book asthma related tests, download Dr Lal PathLabs app today!

FAQs

1. What is the purpose of PFT tests?
   Pulmonary function test is a lung capacity test to help doctors check how well the lungs are working. They check how much air the lungs can hold, how quickly a person can breathe in and out, and how well the lungs move oxygen into the blood and remove carbon dioxide.
2. When is a pulmonary function test required?
   A doctor may suggest a pulmonary function test if a person has ongoing breathing problems, wheezing, or coughing, or if there is a family history or risk of lung conditions like asthma.