Starting this month, the Cystic Fibrosis Foundation is changing the way it reports the lung function of people with cystic fibrosis in the CF Foundation Patient Registry. Historically, the lung function of a person with cystic fibrosis has been compared to average lung function for a healthy person with similar characteristics, including biological sex, age, height, and race. As of April 19, the CF Foundation will no longer use race as a factor in these comparison calculations for lung function data reported to the Registry.
Importantly, this change only reflects a shift in how lung function is reported. It does not reflect a change in individuals’ actual lung function.
The change follows a 2023 American Thoracic Society (ATS) recommendation that race-neutral reference equations — equations that do not use race as a factor in the calculation of average lung function in healthy people — be used to interpret spirometry results. The ATS recommendation was based on recent scientific evidence that shows race-neutral equations are superior for assessing lung function.
Spirometry is a common type of pulmonary function test (PFT) used for many types of lung conditions. The race-neutral reference equations were developed by the Global Lung Function Initiative (GLI) and are referred to as GLI 2022.
Reasoning Behind the Change
The ATS concluded that using race in PFT equations could not be justified scientifically and may promote disparities in diagnosis and management of lung disease. Specifically, the use of race-specific equations has resulted in an underestimation of lung disease for Black individuals, leading to delays in diagnosis and treatment in some cases. The race-neutral equations are intended to help correct the inequities that could result from interpreting spirometry data differently by race.
The use of race-neutral equations may help care teams better understand the severity of patients’ lung disease and determine the best treatment approach. The CF Foundation recommends adoption of GLI 2022 throughout the CF care center network, but recognizes the decision is at the discretion of individual PFT labs and timing may vary. PFT labs are often operated separately from CF programs within hospitals.
How People With CF May Be Affected
People with CF may see changes to their spirometry results — namely, within a metric of lung function called percent predicted — as PFT labs across the U.S. adopt the GLI 2022 reference equations.
When spirometry is done in people with CF, several measurements are taken. One measurement is the amount of air the person can forcefully breathe out in one second. This is called “forced expiratory volume exhaled in the first second,” or FEV1. The FEV1 measurement is then transformed into a percentage of what is predicted to be normal (percent predicted) based on the reference equations.
The earlier race-specific equations assumed that the estimated healthy FEV1 for a Black person was smaller than the estimated healthy FEV1 for a white person. As a result, a Black person would have a higher percent predicted compared to a white person, even though both could report the same absolute FEV1 for the same age, sex, and height combination.
When the new race-neutral equations are used, the CF Foundation expects that most Black people with CF may see an average decrease of 7 percentage points in their FEV1 percent predicted, and most white people with CF may see an average increase of 5 percentage points. For any single person, the change in their FEV1 percent predicted using the new equations will depend on their sex, age, and height as well as their FEV1.
People who identify as other races may see changes too. The direction and magnitude of the changes will depend on how their PFT labs have historically classified their race as well as their sex, age, and height.
Again, these changes only reflect changes in how lung function is interpreted and reported. They do not reflect changes in an individual’s actual lung function. Still, these changes may affect individuals’ referral for lung transplant, eligibility for clinical trials, and overall treatment plans. The CF Foundation also recognizes that any changes in FEV1 percent predicted may be meaningful to individuals, even if it does not affect their clinical care.
It is important to remember that FEV1 percent predicted is just one measure of lung health. Any discussion of an individual’s lung health and treatment plan should consider FEV1 percent predicted in the context of how often the person gets sick, respiratory culture growth, and other measures of health.
The CF Foundation encourages people with CF to bring questions about these changes to their care teams. This handout includes basic information about the changes and sample questions that people with CF may want to ask.