Time to Eliminate Race Adjustments in Spirometry?

By Maggie InmanReviewed by Ware Kuschner, MD, Professor of Medicine, Division of Pulmonary, Allergy, & Critical Care Medicine, Stanford University School of Medicine

Race-based spirometry equations may not be accurate for predicting emphysema in Black patients, according to a recent study in the Annals of Internal Medicine.

Investigators from Northwestern University Feinberg School of Medicine, led by Dr. Gabrielle Liu, conducted a secondary analysis of the CARDIA (Coronary Artery Risk Development In Young

Adults) lung study, a multicenter, population-based, longitudinal cohort study, to determine the difference in emphysema prevalence between Black and White adults with different measures of

normal spirometry results. They used clinical data and spirometry obtained in 2015-2016 and computed tomographic (CT) scans done in 2010-2011. Self-identified race and visually identified

emphysema on CT were compared with spirometry results calculated using standard race-specific and race-neutral reference equations.1

Overall, 2674 participants who received both a CT scan and spirometry were included in the analysis. Of these, 485 were Black men, 762 were Black women, 659 were White men, and 768 were

White women. A total of 6.5% of patients with a race-specific forced expiratory volume in 1 second (FEV1) between 80% and 99% of predicted had emphysema. Among them, the prevalence of

emphysema was 15.5% in Black men versus 4.0% in White men (3.9-fold higher; 95% CI, 2.1- to 7.1-fold). The difference was much smaller among women, 6.6% in Black women versus 3.4% in White

women (1.9-fold higher; 95% CI, 1.0- to 3.8-fold).1

Four percent of patients with a race-specific FEV1 between 100% and 120% of predicted had emphysema. Among these, Black men had a 6.4-fold (95% CI, 2.2- to 18.7-fold) higher prevalence of

emphysema compared with White men (13.9% vs 2.2%) and Black and White women had a similar prevalence (2.6% and 2.0%, respectively). When race-neutral equations were used to identify patients

with an FEV1 percent of predicted between 80% and 120%, racial differences in emphysema prevalence were attenuated among men and eliminated among women.1

The authors noted that spirometry and CT scans were not obtained at the same time and that no clinical data were available after the 2015-2016 visit. They concluded that emphysema is often

present before spirometry results become abnormal, especially among Black men, and that using spirometry alone to differentiate lung health from lung disease may result in underrecognition

of impaired respiratory health.1

The authors comment that “the use of race-neutral equations to interpret spirometry attenuates the racial disparity in emphysema prevalence among those with ‘normal’ results but does not

eliminate it. These findings magnify the need to reconsider the use of race-specific spirometry reference equations in favor of race-neutral equations.” They called for visual emphysema to

be included in definitions of early chronic obstructive pulmonary disease and for CT imaging to be incorporated into the evaluation of patients with suspected impaired respiratory health and

normal spirometry findings.1

Evidence that race-based adjustments in classifying normal spirometric values can lead to disproportionate underrecognition of impaired respiratory health in Black Americans could, in turn,

lead to delayed therapeutic interventions and disproportionately lower access to healthcare and social resources.1