Table 2.
Association of prebronchodilator and postbronchodilator spirometric measures with chronic bronchitis, dyspnoea scores, chest CT emphysema and air trapping and distance covered in 6 min walk test
| Prebronchodilator FEV1/FVC <0.7 (PREO) | Postbronchodilator FEV1/FVC <0.7 (POSTO) | |||||
| OR (95% CI) | P value | AIC | OR (95% CI) | P value | AIC | |
| Chronic bronchitis | 2 (1.78 to 2.25) | <0.001 | 8910 | 2.14 (1.9 to 2.41) | <0.001 | 8882 |
| Coef (95% CI) | P value | AIC | Coef (95% CI) | P value | AIC | |
| MMRC | 0.72 (0.66 to 0.77) | <0.001 | 4849 | 0.85 (0.79 to 0.9) | <0.001 | 4605 |
| SGRQ | 13 (12.16 to 13.83) | <0.001 | 59 145 | 15.3 (14.5 to 16.14) | <0.001 | 58 811 |
| Emphysema, %* | 8.4 (7.9 to 8.9) | <0.001 | 24 259 | 9.79 (9.29 to 10.29) | <0.001 | 23 892 |
| Gas trapping, %*† | 20.2 (19.24 to 21.18) | <0.001 | 27 241 | 23 (22 to 23.9) | <0.001 | 26 738 |
| 6-MWD, feet | −137.4 (−152.9 to 121.9) | <0.001 | 115 774 | −172.8 (−188.3 to 157.2) | <0.001 | 115 608 |
| Prebronchodilator FEV1% predicted | Postbronchodilator FEV1% predicted | |||||
| OR (95% CI) | P value | AIC | OR (95% CI) | P value | AIC | |
| Chronic bronchitis | 0.98 (0.98 to 0.99) | <0.001 | 8833 | 0.98 (0.98 to 0.99) | <0.001 | 8833 |
| Coef (95% CI) | P value | AIC | Coef (95% CI) | P value | AIC | |
| MMRC | −0.026 (−0.027 to 0.025) | <0.001 | 3150 | −0.026 (−0.027 to 0.025) | <0.001 | 3065 |
| SGRQ | −0.44 (−0.46 to 0.43) | <0.001 | 57 014 | −0.45 (−0.46 to 0.43) | <0.001 | 56 967 |
| Emphysema, %* | −0.23 (−0.24 to 0.22) | <0.001 | 22 926 | −0.24 (−0.25 to 0.23) | <0.001 | 22 827 |
| Gas trapping, %*† | −0.52 (−0.53 to 0.50) | <0.001 | 25 519 | −0.52 (−0.53 to 0.5) | <0.001 | 25 471 |
| 6-MWD, feet | 6.35 (6.07 to 6.64) | <0.001 | 114 300 | 6.61 (6.3 to 6.9) | <0.001 | 1 14 144 |
All regression models included the following covariates: age, sex, race, smoking status, pack per years, history (per questionnaire) of asthma, diabetes, high blood pressure, stroke and sleep apnoea.
*For emphysema and gas trapping analysis, data were available for 5553 and 4945 subjects, respectively.
†Gas trapping was measured at functional residual capacity.
6-MWD, 6 min walk distance; AIC, Akaike information criterion; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; MMRC, modified Medical Research Council dyspnoea score; SGRQ, St. George’s Respiratory Questionnaire score.