Rethinking the Race Adjustment in Pulmonary Function Testing

Race-Neutral Equations and Pulmonary Function Test Interpretation in Two Pediatric Cohorts

OBJECTIVE

To investigate the changes in predicted lung function measurements when using race-neutral equations in children, based upon the new Global Lung Initiative (GLI) reference equations, utilizing a race-neutral approach in interpreting spirometry results compared with the 2012 race-specific GLI equations.

STUDY DESIGN

We analyzed data from 2 multicenter prospective cohorts comprised of healthy children and children with history of severe (requiring hospitalization) bronchiolitis. Spirometry testing was done at the 6-year physical exam, and 677 tests were analyzed using new GLI Global and 2012 GLI equations. We used multivariable logistic regression, adjusted for age, height, and sex, to examine the association of race with the development of new impairment or increased severity (forced expiratory volume in the first second (FEV1) z-score ≤ -1.645) as per 2022 American Thoracic Society (ATS) guidelines.

RESULTS

Compared with the race-specific GLI, the race-neutral equation yielded increases in the median forced expiratory volume in the first second and forced vital capacity (FVC) percent predicted in White children but decreases in these two measures in Black children. The prevalence of obstruction increased in White children by 21%, and the prevalence of possible restriction increased in Black children by 222%. Compared with White race, Black race was associated with increased prevalence of new impairments (aOR 7.59; 95%CI, 3.00-19.67; P < .001) and increased severity (aOR 35.40; 95%CI, 4.70-266.40; P = .001). Results were similar across both cohorts.

CONCLUSIONS

As there are no biological justifications for the inclusion of race in spirometry interpretation, use of race-neutral spirometry reference equations led to an increase in both the prevalence and severity of respiratory impairments among Black children.

Historic Use of Race-Based Spirometry Values Lowered Transplant Priority for Black Patients

BACKGROUND

The lung allocation score (LAS) is a tool used to prioritize patients for lung transplantation. For patients with interstitial lung diseases (ILDs), spirometry data are used for the LAS calculation. Spirometry values such as a FVC are subjected to race-specific equations that determine expected values. The effect of race-specific equations in LAS score remains unknown.

RESEARCH QUESTION

Did the use of a race-based spirometry equation lead to longer waitlist times for Black patients?

STUDY DESIGN AND METHODS

We performed a retrospective analysis of patients listed for lung transplantation from 2005 through 2020 using publicly available data from the United Network for Organ Sharing. We recalculated LAS scores for Black patients using White-specific equations with the available variables. The primary objective was to evaluate the effect of race-specific equations on LAS scores and time on the transplant waitlist.

RESULTS

A total of 33,845 patients listed for lung transplantation were included in the analysis. White patients were listed at lower LAS scores, a higher proportion of White patients underwent transplantation, and White patients died on the waitlist at lower rates. When recalculating LAS scores using White-specific equations, Black patients with ILD had up to a 1.9-point higher score, which resulted in additional waitlist time.

INTERPRETATION

Race-specific equations led to longer wait times in Black patients listed for lung transplantation. The use of race-based equations widened already known disparities in pulmonary transplantation.

Early Evidence of Chronic Obstructive Pulmonary Disease Obscured by Race-Specific Prediction Equations

Rationale: The identification of early chronic obstructive pulmonary disease (COPD) is essential to appropriately counsel patients regarding smoking cessation, provide symptomatic treatment, and eventually develop disease-modifying treatments. Disease severity in COPD is defined using race-specific spirometry equations. These may disadvantage non-White individuals in diagnosis and care. Objectives: Determine the impact of race-specific equations on African American (AA) versus non-Hispanic White individuals. Methods: Cross-sectional analyses of the COPDGene (Genetic Epidemiology of Chronic Obstructive Pulmonary Disease) cohort were conducted, comparing non-Hispanic White (n = 6,766) and AA (n = 3,366) participants for COPD manifestations. Measurements and Main Results: Spirometric classifications using race-specific, multiethnic, and "race-reversed" prediction equations (NHANES [National Health and Nutrition Examination Survey] and Global Lung Function Initiative "Other" and "Global") were compared, as were respiratory symptoms, 6-minute-walk distance, computed tomography imaging, respiratory exacerbations, and St. George's Respiratory Questionnaire. Application of different prediction equations to the cohort resulted in different classifications by stage, with NHANES and Global Lung Function Initiative race-specific equations being minimally different, but race-reversed equations moving AA participants to more severe stages and especially between the Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 0 and preserved ratio impaired spirometry groups. Classification using the established NHANES race-specific equations demonstrated that for each of GOLD stages 1-4, AA participants were younger, had fewer pack-years and more current smoking, but had more exacerbations, shorter 6-minute-walk distance, greater dyspnea, and worse BODE (body mass index, airway obstruction, dyspnea, and exercise capacity) scores and St. George's Respiratory Questionnaire scores. Differences were greatest in GOLD stages 1 and 2. Race-reversed equations reclassified 774 AA participants (43%) from GOLD stage 0 to preserved ratio impaired spirometry. Conclusions: Race-specific equations underestimated disease severity among AA participants. These effects were particularly evident in early disease and may result in late detection of COPD.

Use of the Spirometric "Fixed-Ratio" Underdiagnoses COPD in African-Americans in a Longitudinal Cohort Study

BACKGROUND

COPD diagnosis is tightly linked to the fixed-ratio spirometry criteria of FEV1/FVC < 0.7. African-Americans are less often diagnosed with COPD.

OBJECTIVE

Compare COPD diagnosis by fixed-ratio with findings and outcomes by race.

DESIGN

Genetic Epidemiology of COPD (COPDGene) (2007-present), cross-sectional comparing non-Hispanic white (NHW) and African-American (AA) participants for COPD diagnosis, manifestations, and outcomes.

SETTING

Multicenter, longitudinal US cohort study.

PARTICIPANTS

Current or former smokers with ≥ 10-pack-year smoking history enrolled at 21 clinical centers including over-sampling of participants with known COPD and AA. Exclusions were pre-existing non-COPD lung disease, except for a history of asthma.

MEASUREMENTS

Subject diagnosis by conventional criteria. Mortality, imaging, respiratory symptoms, function, and socioeconomic characteristics, including area deprivation index (ADI). Matched analysis (age, sex, and smoking status) of AA vs. NHW within participants without diagnosed COPD (GOLD 0; FEV1 ≥ 80% predicted and FEV1/FVC ≥ 0.7).

RESULTS

Using the fixed ratio, 70% of AA (n = 3366) were classified as non-COPD, versus 49% of NHW (n = 6766). AA smokers were younger (55 vs. 62 years), more often current smoking (80% vs. 39%), with fewer pack-years but similar 12-year mortality. Density distribution plots for FEV1 and FVC raw spirometry values showed disproportionate reductions in FVC relative to FEV1 in AA that systematically led to higher ratios. The matched analysis demonstrated GOLD 0 AA had greater symptoms, worse DLCO, spirometry, BODE scores (1.03 vs 0.54, p < 0.0001), and greater deprivation than NHW.

LIMITATIONS

Lack of an alternative diagnostic metric for comparison.

CONCLUSIONS

The fixed-ratio spirometric criteria for COPD underdiagnosed potential COPD in AA participants when compared to broader diagnostic criteria. Disproportionate reductions in FVC relative to FEV1 leading to higher FEV1/FVC were identified in these participants and associated with deprivation. Broader diagnostic criteria for COPD are needed to identify the disease across all populations.

Lung Imaging in COPD Part 2: Emerging Concepts

The diagnosis, prognostication, and differentiation of phenotypes of COPD can be facilitated by CT scan imaging of the chest. CT scan imaging of the chest is a prerequisite for lung volume reduction surgery and lung transplantation. Quantitative analysis can be used to evaluate extent of disease progression. Evolving imaging techniques include micro-CT scan, ultra-high-resolution and photon-counting CT scan imaging, and MRI. Potential advantages of these newer techniques include improved resolution, prediction of reversibility, and obviation of radiation exposure. This article discusses important emerging techniques in imaging patients with COPD. The clinical usefulness of these emerging techniques as they stand today are tabulated for the benefit of the practicing pulmonologist.

Global, Race-Neutral Reference Equations and Pulmonary Function Test Interpretation

Importance

Race and ethnicity are routinely used to inform pulmonary function test (PFT) interpretation. However, there is no biological justification for such use, and it may reinforce health disparities.

Objective

To compare the PFT interpretations produced with race-neutral and race-specific equations.

Design, Setting, and Participants

In this cross-sectional study, race-neutral reference equations recently developed by the Global Lung Function Initiative (GLI) were used to interpret PFTs performed at an academic medical center between January 2010 and December 2020. The interpretations produced with these race-neutral reference equations were compared with those produced using the race and ethnicity-specific reference equations produced by GLI in 2012. The analysis was conducted from April to October 2022.

Main Outcomes and Measures

The primary outcomes were differences in the percentage of obstructive, restrictive, mixed, and nonspecific lung function impairments identified using the 2 sets of reference equations. Secondary outcomes were differences in severity of these impairments.

Results

PFTs were interpreted from 2722 Black (686 men [25.4%]; mean [SD] age, 51.8 [13.9] years) and 5709 White (2654 men [46.5%]; mean [SD] age, 56.4 [14.3] years) individuals. Among Black individuals, replacing the race-specific reference equations with the race-neutral reference equations was associated with an increase in the prevalence of restriction from 26.8% (95% CI, 25.2%-28.5%) to 37.5% (95% CI, 35.7%-39.3%) and of a nonspecific pattern of impairment from 3.2% (95% CI, 2.5%- 3.8%) to 6.5% (95% CI, 5.6%-7.4%) and no significant change in the prevalence of obstruction (19.9% [95% CI, 18.4%-21.4%] vs 19.5% [95% CI, 18.0%-21.0%]). Among White individuals, replacing the race-specific reference equations with the race-neutral reference equations was associated with a decrease in the prevalence of restriction from 22.6% (95% CI, 21.5%-23.6%) to 18.0% (95% CI, 17.0%-19.0%), a decrease in the prevalence of a nonspecific pattern of impairment from 8.7% (95% CI, 7.9%-9.4%) to 4.0% (95% CI, 3.5%-4.5%), and no significant change in the percentage with obstruction from 23.9% (95% CI, 22.8%-25.1%) to 25.1% (95% CI, 23.9%- 26.2%). The race-neutral reference equations were associated with an increase in severity in 22.8% (95% CI, 21.2%-24.4%) of Black individuals and a decrease in severity in 19.3% (95% CI, 18.2%-20.3%) of White individuals vs the race-specific reference equations.

Conclusions and Relevance

In this cross-sectional study, the use of race-neutral reference equations to interpret PFTs resulted in a significant increase in the number of Black individuals with respiratory impairments along with a significant increase in the severity of the identified impairments. More work is needed to quantify the effect these reference equations would have on diagnosis, referral, and treatment patterns.

A Race-neutral Approach to the Interpretation of Lung Function Measurements

Rationale: The use of self-reported race and ethnicity to interpret lung function measurements has historically assumed that the observed differences in lung function between racial and ethnic groups were because of thoracic cavity size differences relative to standing height. Very few studies have considered the influence of environmental and social determinants on pulmonary function. Consequently, the use of race and ethnicity-specific reference equations may further marginalize disadvantaged populations. Objectives: To develop a race-neutral reference equation for spirometry interpretation. Methods: National Health and Nutrition Examination Survey (NHANES) III data (n = 6,984) were reanalyzed with sitting height and the Cormic index to investigate whether body proportions were better predictors of lung function than race and ethnicity. Furthermore, the original GLI (Global Lung Function Initiative) data (n = 74,185) were reanalyzed with inverse-probability weights to create race-neutral GLI global (2022) equations. Measurements and Main Results: The inclusion of sitting height slightly improved the statistical precision of reference equations compared with using standing height alone but did not explain observed differences in spirometry between the NHANES III race and ethnic groups. GLI global (2022) equations, which do not require the selection of race and ethnicity, had a similar fit to the GLI 2012 "other" equations and wider limits of normal. Conclusions: The use of a single global spirometry equation reflects the wide range of lung function observed within and between populations. Given the inherent limitations of any reference equation, the use of GLI global equations to interpret spirometry requires careful consideration of an individual's symptoms and medical history when used to make clinical, employment, and insurance decisions.

Origins of Racial and Ethnic Bias in Pulmonary Technologies

Understanding how biases originate in medical technologies and developing safeguards to identify, mitigate, and remove their harms are essential to ensuring equal performance in all individuals. Drawing upon examples from pulmonary medicine, this article describes how bias can be introduced in the physical aspects of the technology design, via unrepresentative data, or by conflation of biological with social determinants of health. It then can be perpetuated by inadequate evaluation and regulatory standards. Research demonstrates that pulse oximeters perform differently depending on patient race and ethnicity. Pulmonary function testing and algorithms used to predict healthcare needs are two additional examples of medical technologies with racial and ethnic biases that may perpetuate health disparities.

Research race-specific reference values and lung function impairment, breathlessness and prognosis: Analysis of NHANES 2007-2012

BACKGROUND

Spirometry reference values differ by race/ethnicity, which is controversial. We evaluated the effect of race-specific references on prevalence of lung function impairment and its relation to breathlessness and mortality in the US population.

METHODS

Population-based analysis of the National Health and Nutrition Examination Survey (NHANES) 2007-2012. Race/ethnicity was analyzed as black, white, or other. Reference values for forced expiratory volume in one second (FEV₁) and forced vital capacity (FVC) were calculated for each person using the Global Lung Initiative (GLI)-2012 equations for (1) white; (2) black; and (3) other/mixed people. Outcomes were prevalence of lung function impairment (< lower limit of normal [LLN]), moderate/severe impairment (< 50%pred); exertional breathlessness; and mortality until 31 December, 2015.

RESULTS

We studied 14,123 people (50% female). Compared to those for white, black reference values identified markedly fewer cases of lung function impairment (FEV₁) both in black people (9.3% vs. 36.9%) and other non-white (1.5% vs. 9.5%); and prevalence of moderate/severe impairment was approximately halved. Outcomes by impairment differed by reference used: white (best), other/mixed (intermediate), and black (worst outcomes). Black people with FEV₁ ≥ LLN_black but < LLN_white had 48% increased rate of breathlessness and almost doubled mortality, compared to blacks ≥ LLN_white. White references identified people with good outcomes similarly in black and white people. Findings were similar for FEV₁ and FVC.

CONCLUSION

Compared to using a common reference (for white) across the population, race-specific spirometry references did not improve prediction of breathlessness and prognosis, and may misclassify lung function as normal despite worse outcomes in black people.

Racial and Ethnic Minorities Have a Lower Prevalence of Airflow Obstruction than Non-Hispanic Whites

Racial and ethnic disparities in chronic obstructive pulmonary disease (COPD) are not well-studied. Our objective was to examine differences in limited COPD-related outcomes between three minority groups-African Americans (AAs), Hispanics, and American Indians (AIs) versus non-Hispanic Whites (NHWs), as the referent group, in separate cohorts. Separate cross-sectional evaluations were performed of three US-based cohorts of subjects at risk for COPD: COPDGene Study with 6,884 NHW and 3,416 AA smokers; Lovelace Smokers' Cohort with 1,598 NHW and 378 Hispanic smokers; and Mining Dust Exposure in the United States Cohort with 2,115 NHW, 2,682 Hispanic, and 2,467 AI miners. Prebronchodilator spirometry tests were performed at baseline visits using standard criteria. The primary outcome was the prevalence of airflow obstruction. Secondary outcomes were self-reported physician diagnosis of COPD, chronic bronchitis, and modified Medical Research Council dyspnea score. All minority groups had a lower prevalence of airflow obstruction than NHWs (adjusted ORs varied from 0.29 in AIs to 0.85 in AAs; p < 0.01 for all analyses). AAs had a lower prevalence of chronic bronchitis than NHWs. In our study, all minority groups had a lower prevalence of airflow obstruction but a greater level of self-reported dyspnea than NHWs, and covariates did not explain this association. A better understanding of racial and ethnic differences in smoking-related and occupational airflow obstruction may improve prevention and therapeutic strategies.