Pulmonary function tests (PFTs) have long been used to diagnose and manage lung disease. You may have heard of spirometry, the most performed PFT, used to help determine if your lung function is within a normal range. If it isn’t, then your healthcare provider will look for reasons why and it may mean that you have a lung disease. If so, you will continue to have PFTs while being treated for your disease to help determine how well the treatment is working.
Knowing how vital testing and subsequent results are for disease management, employment and disability, a task force of healthcare providers took a hard look at how the results were being calculated and came up with a new standardized approach for interpreting results, which has been endorsed by the American Thoracic Society and European Respiratory Society.
The new results prioritize a standardized approach and a race-neutral focus. Let’s break down what that means for you.
Standardization of Pulmonary Function Tests using Z-Scores
“To make PFTs even more accurate, healthcare providers are now using something called z-scores,” says A. Ian Wong, a physician at Durham VA Medical Center. “We used to report lung function as a percent of what we would predict your lung function to be, but now we’ve found a better way to do it.” Z-scores describe how common your lung function numbers are. It sounds a bit similar to the old way, but this slightly different comparison helps providers better understand if your results are within a normal range or if there is something going on that needs more attention.
If your lung function is near or below the expected range, it is an indicator that more evaluation is needed. And if you have low lung function, your z-score helps decide how severe your lung disease is. Knowing this helps providers determine the best treatment at the right time for you.
Another benefit of the change is that z-scores are a global indicator of lung function so that makes it easier to receive consistent care around the world. It’s kind of like how most of the world uses the metric system to measure in meters and grams, but the United States still uses customary units like inches and feet. With two different measuring systems, it’s harder to compare. Because of this, healthcare in the United States always uses the metric system to avoid confusion about medication doses or patient weight. Standardization of z-scores at a global level helps improve patient care.
“In summary, z-scores are a new and consistent way to define your lung function.” Says Dr. Wong. “You should know your numbers to help you better understand your treatment goals and your lung health. Your doctor can help answer any questions you have about this.”
Race-neutral Pulmonary Function Tests
PFTs aren’t used exclusively for patients experiencing symptoms of or having been diagnosed with lung disease. Sometimes PFTs are required by an employer – for example the military or the fire department – to ensure that your lung function remains healthy during employment. There are some cutoffs with certain jobs that require your lung function to be within a particular range to maintain employment, making accurate PFT testing essential.
Another example of how important accurate test results are is that disability claims are approved or declined based, in part, on your PFT results. Or you may qualify – or not – for certain treatments such as a lung transplant based on your results. But how we previously calculated these results was found to be inequitable and a new system emerged.
“It is of utmost importance to conduct PFTs in an equitable and respectful manner,” says Aparna Balasubramanian, a physician at Johns Hopkins. “After reviewing the data, defining normal lung function by race was found to hinder appropriate interpretation of PFT results so it was removed from reference equations.”
In fact, it was found to be that the use of race-based calculations can lead to inaccurate diagnoses and perpetuate health disparities, particularly for minority populations. The medical community was alarmed to learn that including race as part of the prediction of normal lung function was potentially leading to an underdiagnosis of lung disease in minority populations. It also has the potential of contributing to systemic racism within healthcare.
“Simply put, including race in reference equations for PFTs caused harm,” says Dr. Balasubramanian, “Moving forward, medical organizations recommend using race-neutral equations so that lung function is assessed based only on age, sex assigned at birth and height.”
Researchers and healthcare providers are constantly looking at new and better ways to prevent, diagnose and treat disease. Data-based changes are a good thing, even though they can be a bit confusing at first. You can reach out to your healthcare provider for more information on your PFT results and how they impact your treatment plan. You can also call the American Lung Association’s Lung HelpLine at 800-LUNGUSA (option 2) to ask our lung health experts your questions about pulmonary function tests. Learn more about pulmonary function tests at Lung.org/pft.
Blog last updated: May 21, 2025
