Race-Specific Interpretation of Spirometry: Impact on the Lung Allocation Score

Abstract

Rationale: Interpretation of spirometry using race-specific reference equations may contribute to health disparities via underestimation of the degree of lung function impairment in Black patients. The use of race-specific equations may differentially affect patients with severe respiratory disease via the use of percentage predicted forced vital capacity (FVCpp) when included in the lung allocation score (LAS), the primary determinant of priority for lung transplantation. Objectives: To determine the impact of a race-specific versus a race-neutral approach to spirometry interpretation on the LAS among adults listed for lung transplantation in the United States. Methods: We developed a cohort from the United Network for Organ Sharing database including all White and Black adults listed for lung transplantation between January 7, 2009, and February 18, 2015. The LAS at listing was calculated for each patient under race-specific and race-neutral approaches, using the FVCpp generated from the Global Lung Function Initiative equation corresponding to each patient's race (race-specific) or from the Global Lung Function Initiative "other" (race-neutral) equation. Differences in LAS between approaches were compared by race, with positive values indicating a higher LAS under the race-neutral approach. Results: In this cohort of 8,982 patients, 90.3% were White and 9.7% were Black. The mean FVCpp was 4.4% higher versus 3.8% lower among White versus Black patients (P < 0.001) under a race-neutral compared with a race-specific approach. Compared with White patients, Black patients had a higher mean LAS under both a race-specific (41.9 vs. 43.9; P < 0.001) and a race-neutral (41.3 vs. 44.3; P < 0.001) approach. However, the mean difference in LAS under a race-neutral approach was -0.6 versus +0.6 for White versus Black patients (P < 0.001). Differences in LAS under a race-neutral approach were most pronounced for those in group B (pulmonary vascular disease) (-0.71 vs. +0.70; P < 0.001) and group D (restrictive lung disease) (-0.78 vs. +0.68; P < 0.001). Conclusions: A race-specific approach to spirometry interpretation has potential to adversely affect the care of Black patients with advanced respiratory disease. Compared with a race-neutral approach, a race-specific approach resulted in lower LASs for Black patients and higher LASs for White patients, which may have contributed to racially biased allocation of lung transplantation. The future use of race-specific equations must be carefully considered.

Keywords: LAS; race; spirometry; transplant.

Figure 1.

Difference in percentage predicted spirometry between race-specific (RS) and race-neutral (RN) approaches as a function of measured spirometry. The difference in percentage predicted spirometry measures when using an RN compared with an RS approach is shown over the range of actual (measured) spirometry values for White and Black individuals. Positive values indicate higher percentage predicted spirometry under an RN approach. Each point represents an individual at the time of listing. Best fitting linear lines with 95% confidence intervals are presented. Differences in percentage predicted spirometry measures increase as measured lung volumes increase. FEV₁ = forced expiratory volume in 1 second; FVC = forced vital capacity.

Figure 2.

Difference in lung allocation score (LAS) and waiting list urgency between race-specific (RS) and race-neutral (RN) approaches as a function of RS-LAS at listing. (A and B) Differences in (A) LAS and (B) predicted survival without transplantation between the RS and RN approaches are shown over the range of the RS-LAS at listing. The RS-LAS on the x-axis was calculated using percentage predicted forced vital capacity from RS reference equations. Each point represents an individual at the time of listing. Best fitting quadratic lines with 95% confidence intervals are displayed for White and Black individuals. Positive values indicate (A) higher LAS and (B) greater number of predicted days survived under an RN approach.