Table 4 Univariate predictors of high impact factor (> 5)

Effect size (relative risk)

0.66

 0–0.5

1.367 (0.423, 4.415)

 0.5–1

Ref

 > 1

0.774 (0.399, 1.501)

Statistically significant

2.667 (0.962, 7.390)

0.06

Mortality is primary outcome

1.671 (0.554, 5.038)

0.36

Multicenter

2.880 (1.183, 7.011)

0.02

Medical domain

0.07

 Medicine

6.872 (1.180, 40.027)

 Obstetrics

3.325 (0.264, 41.731)

 Pediatrics

1.727 (0.3096, 9.636)

 Surgery

Ref

Any industry funding

2.595 (1.102, 6.111)

0.03

Peer review funding

1.275 (0.489, 3.324)

0.62

Random sequence

1.352 (0.641, 2.852)

0.43

Allocation concealment, clearly adequate (A) or not (BCD)

1.188 (0.616, 2.288)

0.61

Double-blind

1.564 (0.544, 4.503)

0.41

Analysis as randomized

0.09

 Unclear

0.427 (0.158, 1.155)

 As treated

0.320 (0.131, 0.783)

 As randomized

Ref

Sample size (every 10 increase)

1.014 (1.002, 1.026)

0.02

Country

0.84

 Canada/USA

2.651 (0.257, 27.376)

 Europe

2.108 (0.213, 20.864)

 Asia

Ref

 Other

2.000 (0.183, 21.861)