Race-based spirometry equations may miss emphysema in Black patients
An observational study of Black and White patients who had both spirometry and a CT scan found that emphysema is often present before spirometry results become abnormal, especially in Black men, and that using spirometry alone may overestimate respiratory health.
Race-based spirometry equations may not be accurate for predicting lung health in Black patients, according to a recent study.
Researchers from Northwestern University Feinberg School of Medicine conducted a secondary analysis of the CARDIA (Coronary Artery Risk Development In Young Adults) Lung study to determine the difference in emphysema prevalence between Black and White adults with normal spirometry results. They used clinical data and spirometry obtained in 2015 to 2016 and CT scans done in 2010 to 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. The results were published July 19 by Annals of Internal Medicine.
Overall, 2,674 participants who received both a CT scan and spirometry were included in the study. Four hundred eighty-five 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 FEV1 between 80% and 99% of predicted had emphysema. Among them, emphysema prevalence was 15.5% in Black men versus 4.0% in White men (3.9-fold higher; 95% CI, 2.1- to 7.1-fold) and 6.6% in Black women versus 3.4% in White women (1.9-fold higher; 95% CI, 1.0- to 3.8-fold). Four percent of patients with a race-specific FEV1 between 100% and 120% of predicted had emphysema. Of these, Black men had a 6.4-fold (95% CI, 2.2- to 18.7-fold) higher emphysema prevalence than 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.
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 cause underrecognition of impaired respiratory health. “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,” the authors wrote. 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.