Reconsidering the Utility of Race-Specific Lung Function Prediction Equations

Abstract

Rationale: African American individuals have worse outcomes in chronic obstructive pulmonary disease (COPD). Objectives: To assess whether race-specific approaches for estimating lung function contribute to racial inequities by failing to recognize pathological decrements and considering them normal. Methods: In a cohort with and at risk for COPD, we assessed whether lung function prediction equations applied in a race-specific versus universal manner better modeled the relationship between FEV₁, FVC, and other COPD outcomes, including the COPD Assessment Test, St. George's Respiratory Questionnaire, computed tomography percent emphysema, airway wall thickness, and 6-minute-walk test. We related these outcomes to differences in FEV₁ using multiple linear regression and compared predictive performance between fitted models using root mean squared error and Alpaydin's paired F test. Measurements and Main Results: Using race-specific equations, African American individuals were calculated to have better lung function than non-Hispanic White individuals (FEV₁, 76.8% vs. 71.8% predicted; P = 0.02). Using universally applied equations, African American individuals were calculated to have worse lung function. Using Hankinson's Non-Hispanic White equation, FEV₁ was 64.7% versus 71.8% (P < 0.001). Using the Global Lung Initiative's Other race equation, FEV₁ was 70.0% versus 77.9% (P < 0.001). Prediction errors from linear regression were less for universally applied equations compared with race-specific equations when examining FEV₁% predicted with the COPD Assessment Test (P < 0.01), St. George's Respiratory Questionnaire (P < 0.01), and airway wall thickness (P < 0.01). Although African American participants had greater adversity (P < 0.001), less adversity was only associated with better FEV₁ in non-Hispanic White participants (P for interaction = 0.041). Conclusions: Race-specific equations may underestimate COPD severity in African American individuals.Clinical trial registered with www.clinicaltrials.gov (NCT01969344).

Keywords: chronic obstructive pulmonary disease; health disparities; racism; respiratory function tests.

Figure 1.

For each patient-reported outcome (St. George’s Respiratory Questionnaire and COPD Assessment Test), participants’ scores are plotted against percent predicted FEV₁. Separate univariable linear regressions for each self-identified racial group are superimposed. The relationships between symptoms and lung function are more consistent with a universally applied lung function prediction equation (GLI-Other). AA = African American; COPD = chronic obstructive pulmonary disease; GLI = Global Lung Initiative; NHW = non-Hispanic White; SPIROMICS = Sub-Populations and InteRmediate Outcome Measures In COPD Study.

Figure 2.

Each COPD-relevant outcome is organized in a separate descending bracket. Arrows indicate each head-to-head comparison, with the best-performing equation (the lowest RMSE) bolded in the circle beneath. ΔRMSE indicates the difference in RMSE between the two equations being compared, and its values are reflective of the magnitude of the scale of responses in each particular outcome. 6MWT = 6-minute-walk test; CAT = COPD Assessment Test; COPD = chronic obstructive pulmonary disease; GLI-O = Global Lung Initiative’s Other race equation; NHW-H = Hankinson’s Non-Hispanic White equation; Pi10 = quantitative wall thickness for a standard airway; RMSE = root mean square error; SGRQ = St. George’s Respiratory Questionnaire.

Figure 3.

Absolute FEV₁ in milliliters for African American and Non-Hispanic White participants from SPIROMICS at each level of the Adversity–Opportunity Index (AOI). Overlying are the multivariable linear regressions of FEV₁ by AOI, stratified by self-reported race. P for interaction = 0.041 indicating that African American participants do not manifest the same increased FEV₁ with increasing AOI as seen for non-Hispanic White participants. COPD = chronic obstructive pulmonary disease; SPIROMICS = Sub-Populations and InteRmediate Outcome Measures In COPD Study.