Effects of Adoption of Race-Neutral Predictive Equations on Spirometry Results in Children With Sickle Cell Disease.

Background: Lung disease is a major cause of morbidity and mortality in children with sickle cell disease (SCD), a condition that is more common in individuals of African American descent. Spirometry is utilized in monitoring lung health. Recently, the American Thoracic Society recommended the use of race-neutral predictive equations. We aimed to evaluate how the use of race-neutral equations may affect spirometry results and interpretation in children with SCD.

Methods: This retrospective study included children aged 5-21 years with SCD followed at Arkansas Children's Hospital (01/01/2000-06/30/2023) who had completed at least one spirometry. Percent predictive (pp) and z-score values were calculated using race-adjusted and race-neutral predictive equations. Absolute and relative differences were calculated. Percent of subjects with forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC) with z-score <-1.645 and pp < 80%, and FEV₁/FVC z-score < -1.645 were compared. Severity of impairment based on z-score was compared.

Results: One hundred children completed 460 spirometries. Transitioning from race-adjusted to race-neutral equations resulted in [mean (SD)]: a decrease in ppFEV₁ [-9.497% (2.8344)], FEV₁ z-score [-0.723 (0.2286)], ppFVC [-10.08% (3.3440)], FVC z-score [-0.750 (0.2757)], FEV₁/FVC z-score [-0.057 (0.05461)], and an increase in ppFEV₁/FVC [0.2785 (0.3921)]. Transitioning from race-adjusted to race-neutral equations resulted in an increase of impairment for FVC and FEV₁ and a threefold increase in subjects with abnormal values.

Conclusions: Adoption of race-neutral reference equations resulted in a decrease in FEV₁ and FVC values (z-scores and percent predicted) and an increase in severity of impairment.