Table 3

Best post-bronchodilator spirometry values* and classification by GLI and NHANES reference ranges for 1068 participants

Spirometry value
RawMean (SD) FEV1, L2.55 (0.64)
Mean (SD) FVC, L3.16 (0.73)
Mean (SD) FEV1/FVC ratio0.80 (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)
ObstructionFEV1/FVC<LLN GLI African-American11.2 (9.4 to 13.2)
FEV1/FVC<LLN NHANES African-American11.5 (9.6 to 13.5)
FEV1/FVC<LLN NHANES Caucasian9.8 (8.1 to 11.7)
RestrictionFVC <LLN GLI African-American8.1 (6.5 to 9.9)
FVC <LLN NHANES African-American7.7 (6.2 to 9.5)
FVC <LLN NHANES Caucasian49.7 (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.