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Table 5 Associations between recruitment and retention rates and trial characteristics

From: A review of reporting of participant recruitment and retention in RCTs in six major journals

 

Screened and eligible

Eligible and randomised

Randomised and outcome assessed

Factor & level

Median

IQR

Number of studies

Median

IQR

Number of studies

Median

IQR

Number of studies

Study size

         

<200

78

63, 95

25

90

79, 100

26

92

86, 94

32

200–449

71

56, 95

18

93

78, 99

21

92

86, 99

29

450–749

51

33, 64

15

86

66, 97

15

93

84, 98

23

750+

71

41, 80

13

91

85, 100

13

97

89, 100

29

   

p = 0.026

  

p = 0.99

  

p = 0.24

Number of arms

         

2

72

48, 93

56

90

78, 100

59

94

88, 99

89

3+

68

51, 79

15

89

70, 97

16

86

76, 94

24

   

p = 0.33

  

p = 0.75

  

p = 0.0035

Multi-centre?

         

Yes

75

42, 86

44

92

73, 99

47

94

85, 99

79

No

64

50, 94

27

87

78, 100

28

93

88, 96

34

   

p = 0.91

  

p = 0.70

  

p = 0.64

Treatment focus

         

Drug

71

53, 86

29

94

73, 100

30

94

86, 99

56

Surgery

75

48, 99

10

89

63, 100

10

99

92, 100

17

Allied

67

50, 88

17

91

81, 99

18

90

85, 94

18

Other

64

44, 86

15

86

79, 93

17

92

84, 96

22

   

p = 0.89

  

p = 0.56

  

p = 0.014

Control

         

Active

70

51, 86

30

88

74, 95

32

92

85, 98

52

Placebo

68

49, 88

41

94

77, 100

43

93

86, 99

61

   

p = 0.82

  

p = 0.24

  

p = 0.46

Time to assessment

         

0 to 4 weeks

8

33, 86

10

83

63, 94

11

99

93, 100

26

>4 weeks to 6 months

7

51, 78

23

91

81, 100

24

92

87, 94

30

>6 to 18 months

74

40, 93

20

94

72, 99

21

88

79, 98

31

>18 months

75

63, 93

16

91

83, 100

16

95

86, 100

23

   

p = 0.087

  

p = 0.242

  

p = 0.075

Funding

         

Pharma

74

54, 93

28

94

83, 100

29

93

85, 99

56

Government/charity

67

48, 86

38

85

70, 97

40

93

86, 96

49

Internal/unstated

56

51, 56

5

98

94, 100

6

95

91, 100

8

   

p = 0.51

  

p = 0.048

  

P = 0.50

  1. P values were obtained from Mann-Whitney tests (for characteristics with two levels), Kruskal-Wallis tests (three or more unordered levels) or trend tests (three or more ordered levels)