Best post-bronchodilator spirometry values* and classification by GLI and NHANES reference ranges for 1068 participants
| Spirometry value | ||
| Raw | Mean (SD) FEV1, L | 2.55 (0.64) |
| Mean (SD) FVC, L | 3.16 (0.73) | |
| Mean (SD) FEV1/FVC ratio | 0.80 (0.09) | |
| Z-scores† | Mean (SD) FEV1 z-score | −0.38 (1.14) |
| Mean (SD) FVC z-score | −0.19 (1.09) | |
| Mean (SD) FEV1/FVC ratio z-score | −0.37 (1.04) | |
| Classification | % of Population (95% CI) | |
| Obstruction | FEV1/FVC<LLN GLI African-American | 11.2 (9.4 to 13.2) |
| FEV1/FVC<LLN NHANES African-American | 11.5 (9.6 to 13.5) | |
| FEV1/FVC<LLN NHANES Caucasian | 9.8 (8.1 to 11.7) | |
| Restriction | FVC <LLN GLI African-American | 8.1 (6.5 to 9.9) |
| FVC <LLN NHANES African-American | 7.7 (6.2 to 9.5) | |
| FVC <LLN NHANES Caucasian | 49.7 (46.7 to 52.8) | |
†Z-scores calculated using GLI African-American reference ranges.
*For participants with spirometry measured at more than one time point, the best FEV1 and FVC values were analysed.
FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; GLI, global lung initiative; LLN, lower limit of normal.