Many African Americans with clear symptoms of chronic obstructive pulmonary disease (COPD) don’t get a formal diagnosis because current diagnostic tools might not work as well for them, a study finds.

Lung structure differences among African Americans that result in scores higher than the cutoff used to diagnose COPD appear to be behind the misdiagnoses.

In African Americans, “COPD is often missed because they are frequently exposed to various kinds of deprivation that seems to result in smaller lungs with comparatively better airflow,” Elizabeth Regan, MD, PhD, the study’s first author and a researcher at National Jewish Health in Denver, said in a hospital press release. “Now that we’ve revealed the gap, we can start to bridge it,” Regan said, adding “better diagnostic tools will lead to better care for all of our patients, regardless of background.”

The study, “Use of the Spirometric “Fixed-Ratio” Underdiagnoses COPD in African-Americans in a Longitudinal Cohort Study,” was published in the Journal of General Internal Medicine.

COPD is a chronic inflammatory lung disease marked by airway blockage that causes persistent cough and wheezing, and shortness of breath. To diagnose COPD, doctors usually check for a block in airflow by using a spirometry, a test that measures how much and how quickly air can flow in and out of the lungs.

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Shortcomings of ratio criteria in African Americans’ COPD diagnosis

It involves two measurements: the volume of air that can be breathed out in one second (FEV1) and the volume of air that can be forced out of the lungs after taking the deepest breath possible (FVC). If the ratio of FEV1 to FVC (FEV1/FVC) is less than 0.7, it suggests COPD.

“African Americans are less often diagnosed with COPD,” the scientists wrote, but the reasons behind this remain largely unclear, leading researchers in the U.S. to evaluate whether the current fixed FEV1/FVC ratio criteria for COPD diagnosis was accurate for African Americans.

They drew on data from the COPDgene study (NCT00608764), a large ongoing U.S. study that seeks to understand how genetics influence the risk of developing COPD among smokers, and analyzed data from 3,366 African Americans and 6,766 non-Hispanic white people from 21 centers across the U.S. All were smokers or former smokers. Those with a preexisting lung disease other than COPD, except for asthma, were excluded.

The researchers reviewed demographic factors, socioeconomic characteristics, respiratory symptoms, lung imaging data, and mortality.

Using the current spirometry criteria, more African Americans were classified as not having COPD than non-Hispanic white people (70% vs. 49%). This means they had a FEV1/FVC ratio of 0.7 or higher. African Americans were younger (55 vs. 62) and more likely to be current smokers (80% vs. 39%), but their risk of dying in 12 years was similar to that of non-Hispanic white people.

They also had a bigger reduction of FVC relative to that of FEV1, increasing the FEV1/FVC ratio and excluding a COPD diagnosis.

“When the two aspects of spirometry are combined in a mathematic ratio (airflow/lung volume) the number is higher than would otherwise be expected, leading to the conclusion that they do not have COPD or other lung problems,” Regan said.

COPD symptoms in African Americans

Higher FEV1/FVC ratios among African Americans were seen despite the fact that many had symptoms suggestive of COPD and some even had signs of emphysema on computed tomography scans. Emphysema is a severe form of COPD marked by the destruction of the tiny air sacs in the lungs where gas exchanges occur.

To ensure a fair comparison, the researchers matched by age, sex, and smoking status the African Americans and the non-Hispanic white people who didn’t get a formal COPD diagnosis.

Again, African Americans had worse spirometry results, had more or more severe symptoms, and worse diffusing capacity for carbon monoxide (DLCO), which measures how well the lungs can exchange gases.

They scored significantly higher on the BODE index, a measure of body mass, airflow obstruction, shortness of breath, and exercise capacity. Higher scores indicate a lower chance of survival.

African Americans were also more likely to live in areas of poorer socioeconomic conditions than non-Hispanic white people, which may lead to differences in lung development and higher FEV1/FVC ratios.

The findings suggest the current way of diagnosing COPD might not be accurate for African Americans and adds to data from previous COPDGene’s analyses that suggest diagnostic criteria should include more than just spirometry data.

“Disproportionate reductions in FVC relative to FEV1 leading to higher FEV1/FVC were identified in these participants and associated with deprivation [lower socioeconomic conditions],” the researchers wrote. “Broader diagnostic criteria for COPD are needed to identify the disease across all populations.”

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