Table 1.
The Pooled Effect Size and Key Methodological Features Between NITs and Superiority Trials
| Findings (31 meta-analyses with 440 RCTs) | Non-inferiority trials (N = 84) vs superiority trials (N = 326) | P value |
|---|---|---|
| Difference of pooled effect size between NITs and superiority trials | ROR = 1.03 (95% CI, 0.90 to 1.15) | 0.64 |
| Number of meta-analyses with statistically significant difference between NITs and superiority trials | 2/29 (6.90%) | |
| Changes of statistical significance in meta-analysis by adding NITs (from nonsignificant to significant) | 6/29 (20.69%) | |
| Number of meta-analyses with lower I2 or no change on I2 by adding NITs | 25/31 (80.65%) | |
| Absolute difference between log transformed OR from the trials and the pooled log transformed OR* | MD = − 0.03 (95% CI, − 0.10 to 0.05) | 0.53 |
| Being early in the chain of evidence (being chronologically the first 2 studies in a meta-analysis) | OR = 1.43 (95% CI, 0.75 to 2.73) | 0.28 |
| Number of patients | MD = 163.47 (95% CI, − 349.26 to 676.20) | 0.53 |
| Study length (month) | MD = − 5.76 (95% CI, − 16.61 to 5.09) | 0.30 |
| Study sites (multiple vs single) | OR = 0.39 (95% CI, 0.16 to 0.98) | 0.05 |
| Funding source (nonprofit vs for-profit/unclear) | OR = 0.46 (95% CI, 0.16 to 1.32) | 0.15 |
| Trials stopped early (yes vs no/unclear) | OR = 2.73 (95% CI, 0.85 to 8.75) | 0.09 |
| Sequence generation (low risk vs high/unclear risk) | OR = 0.37 (95% CI, 0.18 to 0.78) | 0.01 |
| Allocation concealment (low risk vs high/unclear risk) | OR = 0.34 (95% CI, 0.16 to 0.69) | 0.003 |
| Participants and personnel blinding (low risk vs high/unclear risk) | OR = 0.53 (95% CI, 0.26 to 1.06) | 0.07 |
| Outcome assessment blinding (low risk vs high/unclear risk) | OR = 0.30 (95% CI, 0.13 to 0.72) | 0.01 |
| Incomplete outcome data (low risk vs high/unclear risk) | OR = 0.88 (95% CI, 0.42 to 1.87) | 0.75 |
| Selective reporting (low risk vs high/unclear risk) | OR = 0.36 (95% CI, 0.16 to 0.78) | 0.01 |
| Other sources of bias (low risk vs high/unclear risk) | OR = 1.06 (95% CI, 0.44 to 2.53) | 0.90 |
*A measure of deviation of the pooled effect sizes of NITs/superiority trials to the pooled effect sizes of meta-analyses
MD: mean difference; OR: odds ratio; ROR: rate of odds ratio