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Race-Specific Spirometry May Miss Emphysema Diagnoses

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Over-reliance on spirometry to detect emphysema resulted in missed cases in blacks, especially men, based on a secondary analysis of 2,674 people.

“Over the past few years, there has been a growing debate about the use of race adjustment in diagnostic algorithms and equations commonly used in medicine,” lead author Gabrielle Yi-Hui Liu, MD, said in an interview. “While it used to be common to accept racial or ethnic differences in clinical scores and outcomes as inherent differences between populations, it is now increasingly recognized how racism, socioeconomic status, and environmental exposure can cause these racial differences. Our initial interest in this study was to explore how the use of race-specific spirometry reference equations and the use of spirometry in general can contribute to racial disparities.”

“Previous studies have suggested that the use of race equations in spirometry may exacerbate racial disparities in health outcomes due to insufficient recognition of early disease in black adults, and this study adds to that evidence,” said Suman Pal, MBBS, from the University of New Mexico. Albuquerque, in an interview.
“By examining the crucial ways in which systemic factors in medicine, such as equations for race, exacerbate racial inequities in health care, this study is a timely analysis at a time of national reckoning for structural racism,” said Pal, who was not involved in the study.

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In a study published in Annals of Internal Medicine, Liu and colleagues at Northwestern University in Chicago conducted a secondary analysis of data from the CARDIA Lung (Coronary Artery Risk Development in Young Adults) study.

The primary outcome of the study was the prevalence of emphysema among participants with different measures of normal spirometry, stratified by gender and race. Normal results included a ratio of forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) greater than or equal to 0.7, or greater than or equal to the lower limit of normal. Participants were also stratified by percentage of predicted FEV1 using race-specific benchmark equations, for FEV1 between 80% and 99% of predicted or FEV1 between 100% and 120% of predicted.

The study included 485 black men, 762 black women, 659 white men, and 768 white women who underwent both a CT scan (in 2010-2011) and spirometry (obtained in 2015-2016) as part of the CARDIA study. . The mean age of spirometry participants was 55 years.

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A total of 5.3% of participants had emphysema after stratification by FEV1-FVC ratio. The prevalence was significantly higher in black men compared with white men (12.3% vs 4.0%; relative risk 3.0) and in black women compared with white women (5.0% vs 2.6%; RR 1.9).

The association between black race and emphysema risk persisted but decreased when the researchers used a racially neutral estimate.

When participants were stratified by predicted race-specific FEV1, 6.5% of people with race-specific FEV1 between 80% and 99% had emphysema. After controlling for factors such as age and smoking, emphysema was significantly more common in black men compared to white men (15.5% vs. 4.0%) and in black women compared to white women (6.6% vs. 3 ,four%).

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Race differences persisted in men with race-specific FEV1 between 100% and 120% predicted. Of these, 4.0% had emphysema. The prevalence was significantly higher in black men compared to white men (13.9% vs. 2.2%), but similar between black women and white women (2.6% vs. 2.0%).

The use of race-neutral equations reduced, but did not eliminate, these differences, the researchers said.

The investigators noted that the conclusions were limited by the lack of CT scan data during the same visit as the final spirometry collection. “Given that imaging was obtained 5 years prior to spirometry and emphysema is an irreversible finding, this may have led to an overall underestimation of the prevalence of emphysema.”

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Spirometry alone misses cases

“We were surprised by the significant levels of emphysema we saw among black men in our cohort with normal spirometry,” Liu said in an interview. “We didn’t expect that more than one in eight black men with an FEV1 between 100% and 120% would have emphysema—a rate more than six times higher than white men with the same FEV1 range.”

“One of the takeaways is that we are probably overlooking many people with respiratory health problems or true lung disease by using only spirometry to diagnose COPD,” Liu said. In clinical practice, “Physicians should consider prescribing a CT scan for patients with normal spirometry who have respiratory symptoms such as cough or shortness of breath. If emphysema is found, doctors should discuss reducing any potential risk factors and consider using COPD medications such as inhalers.

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“Our results also support the use of race-neutral reference equations for spirometry interpretation instead of race equations. Racial differences in the incidence of emphysema among people with a “normal” FEV1 [between 80% and 120% predicted], were reduced or eliminated when race-neutral equations were used to calculate FEV1. This suggests that racial equations are normalizing declining lung health in black adults,” Liu explained.

“We need to continue research into additional tools that can be used to assess respiratory status and diagnose COPD, while also keeping in mind how these tools can affect racial differences,” Liu said. “Our study shows that our reliance on spirometry measures such as FEV1/FVC ratio and FEV1 overlooks the range of people with respiratory symptoms and CT evidence of lung disease, and that it disproportionately affects black adults in the United States.” Looking ahead, “it is important to find better tools to identify people with respiratory health problems or early onset disease so that we can detect chronic lung disease before it becomes clinically apparent and patients experience significant lung damage.”

The CARDIA study was supported by the National Heart, Lung, and Blood Institute in collaboration with the University of Alabama at Birmingham, Northwestern University, the University of Minnesota, and the Kaiser Foundation Research Institute. Liu received a grant from the National Institutes of Health. The researchers had no financial conflicts to disclose. Pal had no financial conflicts to report.

This article originally appeared on MDedge.com, part of the Medscape professional network.

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