Early Evidence of COPD Obscured by Race-Specific Prediction Equations

Rationale: Identification of early 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 with race-specific spirometry equations. These may disadvantage non-white individuals in diagnosis and care. Objectives: Determine impact of race-specific equations on African-American (AA) versus non-Hispanic White (NHW) individuals. Methods: Cross-sectional analyses of the COPDGene cohort comparing NHW (N=6766) and AA (N=3366) participants for COPD manifestations. Measurements: Spirometric classifications using race-specific, multi-ethnic and race-reversed prediction equations [National Health and Nutrition Examination Survey (NHANES) and Global Lung Function Initiative (GLI) “Other and Global”] were compared, as were respiratory symptoms, six-minute walk distance (6MWD), CT imaging, respiratory exacerbations, and St. George’s Respiratory Questionnaire (SGRQ). Main Results: Application of different prediction equations to the cohort resulted in different classifications by stage, with NHANES and GLI race-specific equations being minimally different, but “race-reversed” equations moving AA to more severe stages and especially between the GOLD 0 and preserved ratio impaired spirometry (PRISm) groups. Classification using the established NHANES race-specific equations demonstrated that for each GOLD stage 1-4, AA participants were younger, had fewer pack years and more current smoking, but had more exacerbations, lower 6MWD, greater dyspnea and worse BODE scores and SGRQ scores. Differences were greatest in GOLD 1 and 2 stages. Race-reversed equations reclassified 774 AA (43%) from GOLD 0 to PRISm. Conclusions: Race-specific equations underestimate disease severity among AAs. These effects are particularly evident in early disease and may result in late detection of COPD.