Fixed-ratio spirometry misses COPD diagnoses in African American patients

Key takeaways:

• Using fixed-ratio spirometry criteria may underdiagnose COPD in African American individuals.
• African Americans had decreased FVC disproportionate to FEV₁, resulting in an elevated FEV₁/FVC ratio.

A fixed-ratio criteria of FEV₁/FVC less than 0.7 for COPD resulted in fewer diagnoses in African American vs. non-Hispanic white individuals, according to results published in Journal of General Internal Medicine.

“Relying only on spirometry for diagnosing COPD does not do justice to the known manifestations of the disease,” Elizabeth A. Regan, MD, PhD, professor of medicine at National Jewish Health, told Healio. “I expect that most clinicians already recognize the importance of symptoms, and this report allows them to follow their clinical judgement without being focused only on spirometry. For African Americans and other groups with a history of deprivation, moving beyond those criteria could facilitate earlier diagnosis. Initiating targeted smoking cessation efforts and symptom management via early diagnosis could reduce ongoing disparities in care.”

In a multicenter, longitudinal cohort study, Regan and colleagues evaluated 10,198 current/former smokers with a 10 pack-year history or greater from the COPDGene study to see how using fixed-ratio spirometry criteria (FEV₁/FVC < 0.7) differed in the diagnosis of COPD among non-Hispanic white individuals (n = 6,766) and African American individuals (n = 3,366).

Demographics

Compared with non-Hispanic white individuals, African Americans significantly differed in age (54.6 years vs. 62 years), prevalence of current smokers (80% vs. 39%) and smoking pack-years (38.2 vs. 47.2).

In terms of socioeconomic characteristics, more African Americans vs. non-Hispanic whites received a poverty-level annual income (52% vs. 18%), had a lower prevalence of continuing education after high school (43% vs. 70%) and had higher area deprivation index [ADI] scores, which signal residence in deprived neighborhoods (mean score, 55.8 vs. 40.2).

Notably, mortality over 12 years did not differ between both racial groups even after adjustment for several demographic characteristics.

COPD diagnosis by race

COPD, according to the fixed-ratio criteria, was less prevalent in African American individuals vs. non-Hispanic white individuals (30% vs. 51%).

Researchers used Global Initiative for Obstructive Lung Disease (GOLD) categories to assess COPD in their population, creating a category they called “GOLD 0” to encompass the group with an FEV₁/FVC of 0.7 or greater and an FEV₁ percent predicted of 80% or greater. Those with only the former but an FEV₁ percent predicted of less than 80% were categorized as “PRISm.”

A greater proportion of African American than non-Hispanic white individuals in this cohort were categorized as GOLD 0 (54% vs. 38%) and PRISm (16% vs. 11%), having failed to meet the criteria for COPD. This resulted in 70% of African Americans and only 49% of non-Hispanic whites grouped into these categories that are not linked to a COPD diagnosis.

When plotting raw spirometry values on density distribution plots, researchers found that African American individuals had “disproportionate reductions in FVC relative to FEV₁” compared with non-Hispanic whites (between-group difference in FEV₁ = 170 mL; FVC = 310 mL), and this resulted in heightened FEV₁/FVC.

“There were a number of African American participants whose lung volume (FVC) was lower on average than what would be usual for a non-Hispanic white person,” Regan told Healio. “This meant that these African American participants would need to have worse airflow or FEV₁ than a similar non-Hispanic white person in order to be considered to have COPD.”

Researchers also observed that both non-Hispanic white and African American individuals had reduced measures of lung function with ADI scores above vs. below the 50th percentile index value (mean FEV₁ = 2.79 vs. 2.88; P = .0007; mean FVC = 3.54 vs. 3.7; P < .0001). Further, residing in an area with high deprivation impacted FVC (difference, 160 mL) more than FEV₁ (difference, 90 mL).

GOLD 0 characteristics

Researchers then conducted an analysis that matched African American and non-Hispanic white individuals from the GOLD 0 cohort based on age, sex and smoking status (n = 1,123 each) and found poorer characteristics in African Americans. These characteristics included:

• more use of respiratory medications (18% vs. 14%; P = .03);
• more scores of two or higher on the Modified Medical Research Council dyspnea scale (35% vs. 21%; P < .0001);
• shorter 6-minute walk distances (1,356 feet vs. 1,551 feet; P < .0001);
• more severe exacerbations (7% vs. 5%; P = .02);
• poorer St. George’s Respiratory Questionnaire total scores (21.1 vs. 18.1; P = .0002);
• worse diffusing capacity of the lungs for carbon monoxide (78.1 vs. 89.6; P < .0001);
• high prevalence of emphysema (centrilobular, 30% vs. 25%; P = .02; paraseptal, 19% vs. 12%; P < .0001);
• higher BODE scores at enrollment (1.03 vs. 0.54) and at 5 years (1.2 vs. 0.59; P < .0001 for both); and
• higher COPD Disease Scores (1.5 vs. 1; P < .0001).

“We found that those ‘not COPD’ African Americans had symptoms consistent with COPD and appeared ‘sicker’ than the non-Hispanic white people who were in the same category of normal spirometry,” Regan told Healio. “We found that they had more dyspnea, exacerbations and worse walking distance. A number of them had emphysema present on their CT scans but were ‘normal’ for the fixed ratio. On further study we found reports from various countries and populations that linked small FVC with social and nutritional deprivation.

“Thus, we have concluded that some portion of any group may be misclassified as healthy, not COPD if they have had a history of factors like social deprivation that reduces the lung volume or FVC,” Regan added. “In the U.S. and in our research population, that is more likely to occur in African American and other medically underserved groups.”

Regan told Healio this research will likely not change how clinicians currently diagnosis COPD but hopes that it will help raise awareness for missed diagnoses in African American individuals.

“From a research perspective, this is likely to remain confusing and controversial for the future because there is no alternative ‘gold’ standard for diagnosis of COPD,” Regan said. “However, for clinical practice I hope that our findings can bring greater recognition of COPD in the African American community and result in better care.

“We are expanding our understanding of social determinants of health for our population in order to recognize the relationship of those experiences in their risk of disease and progression of disease,” Regan added. “It is a complex situation.”

For more information:

Elizabeth A. Regan, MD, PhD, can be reached at regane@njhealth.org.