FEV1Q: a Race-neutral approach to assessing lung function.

RATIONALE: FEV1Q is a simple approach to spirometry interpretation that compares measured lung function to a lower boundary. This study evaluated how well FEV1Q predicts survival compared to current interpretation methods and whether race impacts FEV1Q.

METHODS: White and Black adults with complete spirometry and mortality data from the National Health and Nutrition Examination Survey (NHANES) III and United Network for Organ Sharing (UNOS) database for lung transplant referrals were included. FEV1Q was calculated as forced expiratory volume in one second (FEV1) divided by 0·4 L for females or 0·5 L for males. Cumulative distributions of FEV1 were compared across races. Cox proportional hazard models tested mortality risk from FEV1Q adjusting for age, sex, height, smoking, income, and among UNOS individuals, referral diagnosis. Harrell's C-statistics were compared between absolute FEV1, FEV1Q, FEV1/height2 , FEV1 z-scores and FEV1% predicted. Analyses were stratified by race.

RESULTS: Among 7182 individuals from NHANES and 7149 from UNOS, 1907 (27%) and 991 (14%) were Black respectively. The lower boundary FEV1 values did not differ between Black and White individuals in either population (FEV1 1st percentile difference: ≤0·01 L; p-value>0·05). Decreasing FEV1Q was associated with increasing hazard ratio (HR) for mortality (NHANES HR 1·33, 95% CI 1·28-1·39; UNOS HR 1·18, 95% CI 1·12-1·23). The associations were not confounded nor modified by race. Discriminative power was highest for FEV1Q compared to alternative FEV1 approaches in both Black and White individuals.

CONCLUSIONS: FEV1Q is an intuitive and simple race-neutral approach to interpreting FEV1 that predicts survival better than current alternative methods.