Race-Based Spirometry May Lead to Missed Diagnoses

SAN FRANCISCO — It may be time to move beyond relying largely on spirometry to distinguish between healthy and abnormal lung function in diverse populations.

That conclusion comes from investigators who looked at patients with ostensibly normal spirometry values in a large population-based study and found that using standard equations to adjust for racial differences in lung-function measures appeared to miss emphysema in a significant proportion of Black patients.

"Our traditional measures of lung health based on spirometry may be underrecognizing impaired respiratory health in Black adults, and particularly Black men," said lead author Gabrielle Liu, MD, a fellow in the division of pulmonary and critical care medicine at the Northwestern University Feinberg School of Medicine in Chicago.

"CT imaging may be useful in the evaluation of those with suspected impaired respiratory health and normal spirometry," she said in an oral abstract session at the American Thoracic Society International Conference 2022.

Liu and colleagues studied the association between self-identified race and visually identified emphysema among 2674 participants in the Coronary Artery Risk Development in Young Adults (CARDIA) study. The patients had CT scans at a mean age of 50, and spirometry at a mean age of 55.

Racial Differences

The investigators found that among men with forced expiratory volume in 1 second (FEV₁) ranging from 100% to 120% of predicted according to race-adjusted formulas, 14.6% of Black men had emphysema, compared with only 1.7% of White men (P < .001). Respective emphysema rates in Black women and White women were 3.8% and 1.9%; this difference was not statistically significant.

Among patients with FEV₁ 80% to 99% of predicted according to race-specific measures, 15.5% of Black men had emphysema, compared with 4% of White men (P < .001). Respective rates of emphysema were 6.9% for Black women vs. 3.2% for White women (P = .025).

When the investigators applied race-neutral spirometry reference equations to the same population, they found that it attenuated but did not completely eliminate the racial disparity in emphysema prevalence among patients with FEV₁ ranging from 80% to 120% of predicted.

Relic of the Past

The results suggest that race-based adjustments of spirometry measures are a relic of less enlightened times, said Adam Gaffney, MD, MPH, assistant professor of medicine at Harvard Medical School in Boston and a pulmonologist and critical care physician at Cambridge Health Alliance in Cambridge, Massachusetts.

"If the average lower lung function of Black people is being driven by adversity, structural racism and deprivation, that means that race-specific equations are normalizing that adversity," he told Medscape Medical News.

"In my opinion, it is time to move beyond race-based equations in clinical pulmonary medicine, particularly in the context of patients with established lung disease in whom use of race-based equations might actually lead to undertreatment," said Gaffney, who was not involved in the study.

Liu agreed that it's time to move to race-neutral measures, and that the whole concept of race-based differences is flawed.

"The long-standing structural inequities in health likely made the reference populations have lower lung function than among Whites," she told Medscape.

Liu said that evaluation of lung function should not rely on spirometry alone, but should also include — when appropriate — CT scans, as well as improved understanding of how symptoms may be predictive for poor outcomes.

The study was supported by grants from the National Institutes of Health. Liu and Gaffney have disclosed no relevant financial relationships.

American Thoracic Society International Conference 2022: Abstract A1010. Presented May 15, 2022.

Neil Osterweil, an award-winning medical journalist, is a long-standing and frequent contributor to Medscape.

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