Table 5.
Spirometry parameters according to different recommended classifications of airflow limitation severity
| Mild | COPD-X (n=35) | GOLD (n=5) | GLI-2012 (n=16) | P value |
| FVC post-BD (L) | 2.98 (2.72, 3.24) | 4.08 (2.67, 5.48) | 3.5 (2.96, 4.03) | 0.034* |
| FVC post-BD (%) | 79.51 (74.24, 84.79) | 107.8 (88.78, 126.82) | 93.19 (85.31, 101.06) | 0.003* |
| FVC post-BD (z) | −1.09 (−1.31, –0.86) | 1.18 (−0.28, 2.64) | 0.07 (−0.52, 0.66) | <0.001* |
| FEV1 post-BD (L) | 1.94 (1.77, 2.12) | 2.76 (1.86, 3.66) | 2.32 (1.94, 2.69) | 0.024* |
| FEV1 post-BD (%) | 67.63 (65.77, 69.49) | 92.6 (77.53, 107.67) | 78.63 (71.78, 85.47) | <0.001* |
| FEV1 post-BD (z) | −2.06 (−2.24, –1.88) | −0.23 (−1.18, 0.73) | −1.17 (−1.59, –0.75) | <0.001* |
| FEV1/FVC post-BD (AV) | 0.64 (0.62, 0.66) | 0.68 (0.65, 0.7) | 0.64 (0.61, 0.68) | 0.644 |
| FEV1/FVC post-BD (%) | 83 (80.48, 85.52) | 85.6 (79.29, 91.91) | 84.38 (80.51, 88.24) | 0.479 |
| FEV1/FVC post-BD (z) | −2.34 (−2.57, –2.1) | −1.91 (−2.53, –1.29) | −2.3 (−2.62, –1.98) | 0.737 |
| Moderate | COPD-X (n=96) | GOLD (n=78) | GLI-2012 (n=43) | |
| FVC post-BD (L) | 2.3 (2.16, 2.43) | 2.75 (2.58, 2.91) | 2.61 (2.39, 2.83) | 0.002 |
| FVC post-BD (%) | 62.61 (60.67, 64.56) | 72.97 (70.01, 75.94) | 73.49 (70.64, 76.34) | <0.001* |
| FVC post-BD (z) | −2.54 (−2.69, –2.38) | −1.66 (−1.84, –1.47) | −1.66 (−1.81, –1.5) | <0.001* |
| FEV1 post-BD (L) | 1.4 (1.31, 1.48) | 1.75 (1.64, 1.85) | 1.66 (1.5, 1.82) | <0.001* |
| FEV1 post-BD (%) | 48.46 (47.39, 49.53) | 59.83 (57.99, 61.68) | 59.12 (56.79, 61.44) | <0.001* |
| FEV1 post-BD (z) | −3.32 (−3.42, –3.21) | −2.57 (−2.72, –2.43) | −2.54 (−2.64, –2.45) | <0.001* |
| FEV1/FVC post-BD (AV) | 0.61 (0.59, 0.62) | 0.63 (0.62, 0.64) | 0.62 (0.6, 0.65) | 0.111 |
| FEV1/FVC post-BD (%) | 76.91 (74.37, 79.44) | 80.23 (77.46, 83.01) | 80.47 (78.04, 82.89) | 0.054 |
| FEV1/FVC post-BD (z) | −2.68 (−2.85, –2.5) | −2.43 (−2.59, –2.27) | −2.43 (−2.63, –2.23) | 0.042* |
| Severe | COPD-X (n=102) | GOLD (n=97) | GLI-2012 (n=83) | |
| FVC post-BD (L) | 1.74 (1.64, 1.83) | 2.03 (1.92, 2.14) | 2.31 (2.16, 2.45) | <0.001* |
| FVC post-BD (%) | 45.95 (43.79, 48.11) | 55.8 (53.96, 57.65) | 60 (57.39, 62.61) | <0.001* |
| FVC post-BD (z) | −4.06 (−4.26, –3.86) | −3.14 (−3.31, –2.98) | −2.71 (−2.86, –2.56) | <0.001* |
| FEV1 post-BD (L) | 0.85 (0.8, 0.9) | 1.15 (1.08, 1.21) | 1.37 (1.28, 1.47) | <0.001* |
| FEV1 post-BD (%) | 28.27 (26.87, 29.68) | 39.99 (38.86, 41.12) | 45.1 (43.13, 47.06) | <0.001* |
| FEV1 post-BD (z) | −4.67 (−4.8, –4.54) | −3.87 (−3.98, –3.75) | −3.49 (−3.56, –3.42) | <0.001* |
| FEV1/FVC post-BD (AV) | 0.5 (0.48, 0.52) | 0.57 (0.55, 0.59) | 0.59 (0.58, 0.61) | <0.001* |
| FEV1/FVC post-BD (%) | 61.85 (59.28, 64.43) | 72.38 (70.21, 74.55) | 73.72 (70.41, 77.04) | <0.001* |
| FEV1/FVC post-BD (z) | −3.95 (−4.13, –3.78) | −3.13 (−3.32, –2.95) | −2.88 (−3.05, –2.71) | <0.001* |
| Very severe | COPD-X | GOLD (n=58) | GLI-2012 (n=96) | |
| FVC post-BD (L) | 1.57 (1.45, 1.68) | 1.75 (1.65, 1.85) | 0.024* | |
| FVC post- BD (%) | 40.97 (38.29, 43.64) | 46.79 (44.59, 48.99) | 0.001* | |
| FVC post-BD (z) | −4.51 (−4.75, –4.27) | −4.19 (−4.38, –4.01) | 0.040* | |
| FEV1 post-BD (L) | 0.72 (0.66, 0.77) | 0.89 (0.82, 0.96) | <0.001* | |
| FEV1 post-BD (%) | 23.4 (22, 24.79) | 29.41 (27.73, 31.09) | <0.001* | |
| FEV1 post-BD (z) | −5.02 (−5.16, –4.88) | −4.8 (−4.91, –4.69) | 0.015* | |
| FEV1/FVC post-BD (AV) | 0.47 (0.44, 0.49) | 0.51 (0.49, 0.53) | 0.012* | |
| FEV1/FVC post-BD (%) | 57.21 (53.66, 60.75) | 63.11 (60.56, 65.67) | 0.007* | |
| FEV1/FVC post-BD (z) | −4.28 (−4.5, –4.06) | −3.94 (−4.14, –3.74) | 0.027* |
*Statistically significant.
AV, absolute value; BD, bronchodilator; COPD, chronic obstructive pulmonary disease; COPD-X, concise tool for chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; GLI, global lung initiative; GOLD, global initiative for chronic obstructive lung disease; Z, z-score.