Race-neutral lung function equations impact spirometry interpretation
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Key takeaways:
- Mean FEV1 and FVC percent predicted changed with use of race-neutral vs. race-specific equations.
- The impact of race-neutral equations on spirometry interpretation was greatest among Black individuals.
Use of race-neutral vs. race-specific lung function equations led to different interpretations of spirometry findings, especially among Black individuals, according to study results.
“[Global Lung Function Initiative (GLI)] Global offers a ‘race-neutral’ approach to the interpretation of lung function measurements, motivated by efforts to eliminate health disparities and structural racism in medicine,” Amjad N. Kanj, MD, MPH, pulmonary and critical care fellow at Mayo Clinic in Rochester, Minnesota, and colleagues wrote.
In a multicenter cross-sectional study published in American Journal of Respiratory and Critical Care Medicine, Kanj and colleagues assessed 109,447 individuals with spirometry tests to determine how predicted lung function measurements change with use of GLI Global race-neutral reference equations vs. GLI-2012 race-specific equations.
The total cohort included 101,010 white individuals (mean age, 59.5 years; 51.6% women), 4,476 Black individuals (mean age, 52 years; 58.6% women), 236 Northeast Asian individuals (mean age, 53.9 years; 54.7% women), 1,472 Southeast Asian individuals (mean age, 51.9 years; 52.9% women) and 2,253 mixed/other race individuals (mean age, 48.7 years; 51.1% women).
At baseline, researchers evaluated dyspnea in each group using the modified Medical Research Council (mMRC) scale score and found that 36.7% of Black individuals had a score of two or higher. The highest proportion of individuals meeting this score was found in this group compared with the other four groups.
Researchers also noted differences in absolute FEV1 and FVC percent predicted based on race/ethnicity with use of GLI-2012 reference equations. For white and Northeast Asian individuals, FEV1 was between 2.47 L to 2.51 L and FVC was between 3.19 L to 3.36 L. Black, Southeast Asian and mixed/other race individuals had lower measures of lung function.
White and Northeast Asian individuals continued to have higher measures of mean FEV1 and FVC percent predicted after use of GLI race-neutral equations. For Black, Southeast Asian and mixed/other race individuals, these measures went down, with the greatest decline observed in the Black cohort (FEV1, –8.4%; FVC, –8.6%).
Use of race-neutral vs. race-specific equations further resulted in more Black individuals with possible restriction (33.1% vs. 21.9%). The only other group with an increase in individuals with possible restriction was the Southeast Asian group (19.1% vs. 13.9%).
The cohort of white individuals was the only racial/ethnic group who had more individuals with obstruction after use of race-neutral vs. race-specific equations (21.6% vs. 19.7%).
After representing each group included in this study equally, 10.2% of the total cohort had a different interpretation of lung function results with use of race-neutral vs. race-specific equations. Compared with white, Southeast Asian, Northeast Asian and mixed/other race individuals, more Black individuals had changes in the interpretation of their spirometry test results with the neutral equations, including a higher prevalence of abnormal test results (relative increase, 32.9%).
Lastly, among those with obstruction according to race-neutral vs. race-specific equations, these individuals faced a higher likelihood for an mMRC score of at least two (OR = 1.7; 95% CI, 1.2-2.5) and air trapping (OR = 2.6; 95% CI, 1.4-5.1).
Among those with possible restriction based on race-neutral vs. race-specific equations, researchers found a heightened likelihood for low total lung capacity (OR = 3.3; 95% CI, 2.7-4.2).
“It is crucial to consider the intended use of spirometry interpretation and acknowledge the continued importance of placing these data within an appropriate clinical context,” Kanj and colleagues wrote. “More research is needed to understand the clinical implications of the changes in interpretation we observe using the GLI Global reference equations.”
Perspective
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This study provides important information to clinicians on how the recent changes in the recommended equations for lung function interpretation will impact patients. While the recent shift to using GLI Global as a race-neutral reference equation is an important step toward promoting racial equity among patients with respiratory disease, there is a critical need for clinicians to recognize how the change in equations will impact care. Because of the shift in reference equations, some patients could see a change in their lung function interpretation from “normal” to “abnormal” (or vice versa) despite no change in their actual underlying lung function — just because of the change in equations.
These findings demonstrate that changes in how pulmonologists interpret spirometry may be surprisingly common. Importantly, the types and frequency of these changes in interpretation will strongly depend on a patient’s race. In particular, the results of this study may help clinicians navigate the uncertainty that arises when a patient’s lung function falls close to a diagnostic threshold (ie, just above or below the lower limit of normal). For example, knowing that a patient with a borderline result would have been clearly normal or abnormal under the prior system of equations might help a clinician decide on the necessity of further diagnostic work-up or treatment.
In addition, the study also provides an important suggestion that GLI Global may be more accurate than GLI-2012 because abnormalities identified by GLI-Global seemed to correlate better with other markers of respiratory disease — both in terms of symptoms and other lung function metrics. While the authors themselves note these results are “far from definitive,” they are a reassuring and helpful step in response to previously raised concerns that GLI-Global could lead us to over- or under-diagnose respiratory disease compared to the prior race-specific approach.
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