Summary of meta-analyses for studies with mortality as an outcome, without randomization of potential participants as “insiders” v. “outsiders” (subgroups based on effectiveness of trial treatment)
| Subgroup | No. of trials | No. of events/no. of patients | Weight, % | RR (95% CI) | I2, % | |
|---|---|---|---|---|---|---|
| RCT | Cohort | |||||
| Trial treatment effective, same treatment and comparator given to “outsiders” | 3 | 273/2 000 | 251/2 447 | 15.2 | 1.30 (0.78 to 2.16) | 79 |
| Trial treatment effective, treatment only given to “outsiders” | 1 | 39/47 | 76/97 | 7.0 | 1.06 (0.90 to 1.25) | NA |
| Trial treatment effective, comparator only given to “outsiders” | 1 | 53/62 | 7/10 | 5.0 | 1.22 (0.80 to 1.86) | NA |
| Trial treatment effective, neither treatment nor comparator given to “outsiders” | 2 | 377/2 124 | 116/759 | 12.4 | 1.13 (0.43 to 2.94) | 96 |
| Trial treatment ineffective | 9 | 478/22 306 | 472/10 328 | 44.2 | 0.73 (0.50 to 1.05) | 92 |
| Trial effect or treatment given unknown | 5 | 640/27 175 | 192/12 176 | 16.2 | 0.83 (0.59 to 1.18) | 60 |
| Overall | 21 | 1 860/53 714 | 1 114/25 817 | 100.0 | 0.92 (0.78 to 1.07) | 84 |
Note: CI = confidence interval, NA = not applicable, RCT = randomized controlled trial, RR = relative risk.