Table 4 Trial characteristics and quality assessment stratified by trial registration and overall risk of bias (N = 300)

Impact factor (median, range)

294

4.017 (0.581-52.589)

1.883 (0.080-15.484)

2.948 (0.475-10.169)

1.850 (0.329-52.589)

2.342 (0.080-28.638)

Continent of corresponding author

   Africa

11

4 (5.8)

7 (3.0)

1 (4.4)

4 (4.0)

6 (3.4)

   Asia

58

6 (8.7)

52 (22.5)

6 (26.1)

27 (27.3)

25 (14.0)

   Australia

16

1 (1.5)

15 (6.5)

2 (8.7)

7 (7.1)

7 (3.9)

   Europe (excluding UK)

91

17 (24.6)

74 (32.0)

6 (26.1)

27 (27.3)

58 (32.6)

   North America

87

30 (43.5)

57 (24.7)

5 (21.7)

19 (19.2)

63 (35.4)

   South America

7

2 (2.9)

5 (2.2)

-

2 (2.0)

5 (2.8)

   United Kingdom

30

9 (13.0)

21 (9.1)

3 (13.0)

13 (13.1)

14 (7.9)

Funding source specified

194

62 (89.9)

132 (57.1)

23 (100.0)

49 (49.5)

122 (68.5)

Industry supported

67

24/62 (38.7)

43/132 (32.6)

7/23 (30.4)

8/49 (16.3)

52/122 (42.6)

Primary outcome explicitly stated

123

41 (59.4)

82 (35.5)

14 (60.9)

34 (34.3)

75 (42.1)

Statistically significant outcome

230

47 (68.1)

183 (79.2)

15 (65.2)

83 (83.8)

132 (74.2)

Data Monitoring Committee

14

9 (13.0)

5 (2.2)

1 (4.4)

5 (5.1)

8 (4.5)

Jadad score (mean; median, range)

300

2.99 (3; 0-5)

2.44 (2; 0-5)

3.96 (4; 3-5)

2.24 (2; 1-5)

2.56 (2; 0-5)

Allocation Concealment

   Adequate

65

24 (34.8)

41 (17.8)

20 (87.0)

15 (15.2)

30 (16.9)

   Unclear

227

45 (65.2)

182 (78.8)

3 (13.0)

84 (84.9)

140 (78.7)

   Inadequate

8

-

8 (3.5)

-

-

8 (4.5)

Trial registered

69

NA

NA

11 (47.8)

10 (10.1)

48 (27.0)

Risk of Bias

   Low

23

11 (15.9)

12 (5.2)

NA

NA

NA

   Unclear

99

10 (14.5)

89 (38.5)

   High

178

48 (69.6)

130 (56.3)