Table 1.
Effect of dFEV1 on the Absolute Difference in Exacerbation Rates
| Inclusion | No. of Trials | No. of Comparisons | No. of Subjects | Slope (b) Estimate (95% CI) |
P | R2 |
|---|---|---|---|---|---|---|
| All studies | 94 | 167 | 119,227 | –0.06 (–0.11 to –0.02) | .009 | 0.05 |
| Only two arms | 49 | 49 | 45,371 | –0.14 (–0.26 to –0.02) | .018 | 0.14 |
| BD only | 49 | 76 | 80,718 | –0.12 (–0.19 to –0.05) | .001 | 0.15 |
| ICS only | 27 | 35 | 32,354 | –0.14 (–0.29 to 0.01) | .062 | 0.13 |
| PDE4 only | 13 | 14 | 14,523 | –0.15 (–0.62 to 0.32) | .542 | 0.00 |
| Non-BD | 57 | 91 | 56,715 | –0.02 (–0.09 to 0.05) | .519 | 0.00 |
| ≥1 Exacerbation in the previous year | 27 | 47 | 31,055 | –0.12 (–0.24 to –0.01) | .038 | 0.11 |
For this analysis, the model is rate difference (RD) = a + b*dTreat. “Comparisons” represent an individual experimental vs control comparison within a trial, and “trials” represent the total number of trials. Thus, trials with > 2 arms will have > 1 comparison. The unit for dTreat is 100 mL. BD = bronchodilator; dFEV1 = between-group difference in change in predose (trough) FEV1 from the beginning to the end of the trial; ICS = inhaled corticosteroid; non-BD = nonbronchodilator; PDE4 = phosphodiesterase-4.