Race-neutral spirometry reclassification in self-identified black and white patients

Recent consensus guidelines endorsed using a Global Lung Function Initiative (GLI Global) race-neutral approach to interpret spirometry. This study aims to examine how spirometry results using GLI Global reference equations correlate with patient health care utilization and outcomes in a real-world cohort of patients. Pulmonary function tests (PFTs) were analyzed via race-specific and GLI Global approaches, respectively, using a 2010–2020 retrospective cohort study of spirometry tests. An abnormally low result for either forced vital capacity (FVC) or forced expiratory volume in 1 s (FEV1) was defined as a z-score <−1.645. One year pulmonary medication prescription, outpatient visit, emergency department (ED) visit or hospitalization, as well as all-cause mortality were evaluated. Out of the total cohort of 6107 tests, 530 (9%) and 599 (10%) results were re-classified when switching from race-specific to race-neutral for FEV1 and FVC, respectively. Compared with patients whose lung function was consistently in the normal range (the control group), Black patients who were re-classified with an abnormally low FEV1 had higher health care utilization including pulmonary medication prescriptions, ED visits, and worse outcomes such as hospitalization. White subjects whose FEV1 was re-classified as normal also had worse outcomes including higher mortality than the consistently normal group. Similar results were obtained when analyzing FVC. We conclude that both Black and White subjects whose FEV1 and FVC were re-classified had worse outcomes compared to those who remained normal. Clinical context and judgment must be used when considering any lung function result near arbitrary thresholds of normal.