The impact of switching to race-neutral reference equations on FEV1 percent predicted among people with cystic fibrosis

Abstract

Rationale: The American Thoracic Society recommended switching to race-neutral spirometry reference equations, as race is a social construct and to avoid normalizing disparities in lung function due to structural racism. Understanding the impact of the race-neutral equations on percent predicted forced expiratory volume in one second (ppFEV₁) in people with cystic fibrosis (PwCF) will help prepare patients and providers to interpret pulmonary function test results.

Objective(s): To quantify the impact of switching from Global Lung Initiative (GLI) 2012 race-specific to GLI 2022 Global race-neutral reference equations on the distribution of ppFEV₁ among PwCF of different races.

Methods: Cross-sectional analysis of FEV₁ among PwCF ages ≥6 years in the 2021 U.S. Cystic Fibrosis Foundation Patient Registry. We describe the absolute difference in ppFEV₁ between the two reference equations by reported race and the effect of age and height on this difference.

Results: With the switch to GLI Global, ppFEV₁ will increase for White (median increase 4.7, (IQR: 3.1; 6.4)) and Asian (2.6 (IQR: 1.6; 3.7)) individuals and decrease for Black individuals (-7.7, (IQR: -10.9; -5.2)). Other race categories will see minimal changes in median ppFEV₁. Individuals with higher baseline ppFEV₁ and younger age will see a greater change in ppFEV₁ (i.e., a greater improvement among White and Asian individuals and a greater decline among Black individuals).

Conclusions: Switching from GLI 2012 race-specific reference equations to GLI 2022 Global race-neutral equations will result in larger reductions in ppFEV₁ among Black individuals with CF than increases among White and Asian people with CF.

Keywords: Cystic fibrosis; Forced expiratory volume; Respiratory function tests.