August 7, 2023

A Tool to Help in Transition to “Race-Neutral” PFT Interpretation

A set of graphs helps quantify the expected changes in forced expiratory volume at one second (FEV1), forced vital capacity (FVC) and FEV1/FVC ratio with the new race-neutral equation

spirometry

Now that “race” has been removed as a criterion for the interpretation of spirometry results, Cleveland Clinic pulmonologist Philippe Haouzi, MD has developed a tool to help clinicians make the transition for patients who they’re managing over time.

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In May 2023, the American Thoracic Society (ATS) called for the removal of “race” from pulmonary function test (PFT) equations, recommending instead that the race-neutral Global Lung Function Initiative (GLI) reference equation be used instead. This equation retains age, sex and height as the key variables only. These changes will affect the spirometry data (FEV1, CVF and their ratio). Endorsed by the European Respiratory Society, the official ATS statement was published in the American Journal of Respiratory and Critical Care Medicine.1

Recognizing the need for change

Editor’s note: The term “race” is used throughout the article where necessary in its traditional sense (despite its limitations) for lack of a better term.

Previously, four different groups were considered: white, Black, North East Asia and South East Asia. In keeping with these categories, the predicted normal values were ~15% and ~5-10% lower for self-identified Black and South East Asian patients respectively, than for people identifying as white. There were important implications for the diagnosis and treatment of many lung diseases, considering that lower values of lung volumes were acceptable for self-identified Black and South East Asian patients than for white patients. According to the new ATS statement, there has long been concerns that “use of race and ethnicity in PFT interpretation contributes to a false view of fixed differences between races and may mask the effects of differential exposures.”

In addition, the authors of these new ATS/ERS recommendations wrote, “Normalization of differences with race-specific equations in PFT interpretation potentially contributes to medical harms from the lack of attention to modifiable risk factors for reduced pulmonary function resulting from racism.”

Dr. Haouzi points out that many factors play a role in pulmonary function, including maternal and early-life nutrition, economic status, geography and environmental exposures to viruses. In addition, the impact of toxic or allergic agents is still poorly understood as individual genetic factors.

“The variability in pulmonary volumes and function due to those factors is certainly much greater than the variability that could be due to ‘race,’ if any,” he explains.

Dr. Haouzi continues, “In addition, the definition of ‘race’ used by the previous GLI references mixes up characteristics such as the color of the skin, the geographical origin of a patient and some unclear “ethnical” criteria. There are certainly, still unknown, genetic determinants in lung volumes but superficial appearance of ‘race’, based on self-identification or geographic origin has no proven bearing on any reliable characteristics of the lung function or volumes.”

The ATS statement provides details about the history and methodology of race-specific reference equations, the rationale for removing race from these equations, and the clinical implications including for people who are near the thresholds that trigger important treatment decisions by averaging the existing data new reference values were established that can now be applied to everyone, regardless of race.

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“These new predicted values affect every patient, although not to the same extent; for instance, they will have a greater impact on those that were the most affected by the previous reference values such as Black patients and the elderly population,” Dr. Haouzi observes.

Easing the transition

What the ATS statement doesn’t do, but which Dr. Haouzi has now tackled, is provide a quantification of the expected changes in FEV1, FVC and FEV1/FVC ratio — information that is essential to the follow-up of patients with chronic lung conditions. In many instances, results that were previously reported as normal or borderline will now be reported as abnormal.

To do this, he used the old and new complex regression equations, which are not straightforward equations, as they require specific sets of discrete values different for each age. Dr. Haouzi would like to acknowledge the help of Jonathan McCully, MHI, who is the system analyst working in the PFT division and who helped obtain these specific sets of data. “Without him, these equations are not usable. We created a set of graphs that display the difference between FEV1, FVC and FEV1/FVC predicted values using the new race-neutral equation and the previous references in keeping with age and height,” explains Dr. Haouzi.

As an example, separate graphs are presented for self-reported Black and white men and women. Two separate lines in each graph represent people with heights of 160 cm (63 inches) and 180 cm (71 inches). Age is presented on the X axis, and the percentage expected changes in predicted PFT values are on the Y axis.

As revealed by these graphs, the groups who will be the most affected when race was used as a criterion, will be Black women above the age of 55. The difference for these patients could be as much as a 20% increase in predicted values. “Since spirometry values below 80% of the predicted are considered low, results that were considered normal three months ago in Black or Southwest Asian patients will now be flagged as possibly reflecting a lung disease that may require treatment or a close follow-up despite the same lung function. In contrast, the impact for patients who self-identified as white will be minimal,” Dr. Haouzi points out.

Incorporating the graphs into care

The above graphs allow a rapid visual determination of the change (relative difference expressed in percent) between the new race-neutral and the previous race-based predicted FEV1 and FVC, according to the age at different heights.

To help ensure that they are used correctly and effectively, Dr. Haouzi notes a couple of things to be mindful of when using the graphs:

Beware of the sign: As displayed in the above figure, the race-neutral predicted FEV1 for a 55-year-old African American male patient (180 cm), for instance, is ~11 % higher than the “old” predicted race-based FEV1. These graphs can also be used to estimate the change in percent predicted of the race-based measured FEV1 or FVC, knowing the percent predicted of the new race-neutral formula from the new PFT report. This estimation can be simply determined from this patient by multiplying the measured race-neutral percent predicted value by 11% and adding that value to the race-neutral percent predicted. For instance, this patient was found to have a FEV1 of 2.8 l corresponding to 76% of the predicted value using the new race-neutral references. The “old” race-based percent predicted FEV1 was 84% [ (11% X 76%) + 76% = 84%].

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The issue of height: These figures were designed to give an immediate visual estimate of what would be the race-based values corresponding to the new race-neutral results between 160 and 180 cm. Data for patients outside this range will be affected by a few percentage points only and can be obtained from the PFT labs along with data for other races. A similar approach has been used for the lower limit of normal (LLN) and can be provided by the PFT labs.

Looking ahead

The implications for treatment of patients with conditions such as pulmonary fibrosis, for instance, will need to be addressed, as certain groups of Black or Southwest Asian patients who may not have qualified for specific treatment, may now be eligible,” he adds.

“We would advise our colleagues to put these new references into context, take time to look at the absolute value, and use those graphs if needed. Sometimes we need to be reminded that a test is just a test, and it does not tell the whole story,” Dr. Haouzi says.

It’s a complicated transition for some patients, he acknowledges. “We must be aware of the impacts of this new predicted values system. A simple set of graphs would be easy to use during this transition period. If someone can help create a simple application to be used online, I’d be happy to work with them.”

References

  1. Bhakta NR, Bime C, Kaminsky DA, et al. Race and Ethnicity in Pulmonary Function Test Interpretation: An Official American Thoracic Society Statement. Am Thorac Soc. 2023;207(8):978-995.

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