FEV ₁ Q as a race-neutral assessment of lung function in Nepal, Peru and Uganda

Background Forced expiratory volume in 1 s quotient (FEV 1 Q) is a race-neutral expression of lung function. The validity and utility of FEV 1 Q across Global South populations has not been previously explored. Methods We conducted a post-hoc analysis of data from the Global Excellence in COPD Outcomes-1 and -2 (GECo1 and GECo2) studies in which a random age- and sex-stratified population of 10 709 people were recruited in Nepal, Peru and Uganda. The FEV 1 first percentile (used to derive FEV 1 Q) was estimated in those with COPD by site and sex. We examined associations between FEV 1 Q, risk factors and respiratory morbidity. We estimated the rate of decline in FEV 1 Q. We evaluated the discriminative accuracy of FEV 1 Q in diagnosing COPD. Results The first percentiles of FEV 1 in those with COPD, at 0.43 L in women and 0.52 L in men, were similar to those previously used to calculate FEV 1 Q. Lower FEV 1 Q was associated with older age, lower socioeconomic status, shorter height and greater smoking pack-years. We estimated that decline in FEV 1 Q with age was 0.65 (95% CI 0.64–0.67) units per 10 years, and more rapid in those continuing to smoke at 0.82 (95% CI 0.77–0.87) units per 10 years. FEV 1 Q was lower in those with prior respiratory hospitalisations and impairment in daily activities due to respiratory disease, and associated with future hospitalisation risk in the GECo2 study. Pre-bronchodilator FEV 1 Q had reasonable diagnostic accuracy for COPD (area under the curve (AUC) 0.87, 95% CI 0.85–0.88), similar to pre-bronchodilator FEV 1 % predicted (AUC 0.88, 95% CI 0.87–0.90). Conclusion Our data support the validity and utility of FEV 1 Q as a race-neutral approach to lung function assessment in diverse settings, including the Global South where the burden of lung disease is greatest.