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Table 1 Participant characteristics at enrollment for randomized participants and voluntary run-in failures

From: Randomized controlled trials: who fails run-in?

 

Full factorial randomization

Two-group randomization

 

Men (N = 1606)

Women (N = 301)

Women (N = 666)

 

Randomized

Voluntary run-in failure

p

Randomized

Voluntary run-in failure

p

Randomized

Voluntary run-in failure

p

 

N (%)

N (%)

 

N (%)

N (%)

 

N (%)

N (%)

 

Total participants

1423 (89)

183 (11)

 

252 (84)

49 (16)

 

584 (88)

82 (12)

 

PERSONAL FACTORS

 Age mean (SD)

58.8 (6.9)

57.5 (7.1)

0.01

56.6 (6.9)

57.5 (6.0)

0.41

56.8 (6.3)

57.3 (7.2)

0.59

 Race

  

0.02a

  

0.04a

  

0.02a

  White

1214 (90)

140 (10)

 

211 (85)

37 (15)

 

475 (90)

55 (10)

 

  Black

100 (83)

21 (17)

 

31 (86)

5 (14)

 

53 (78)

15 (22)

 

  Asian

35 (88)

5 (12)

 

1 (100)

0 (0)

 

15 (94)

1 (6.3)

 

  Native American

9 (100)

0 (0)

 

2 (67)

1 (33)

 

2 (100)

0 (0)

 

  Pacific Islander

1 (100)

0 (0)

 

1 (100)

0 (0)

 

0 (0)

0 (0)

 

  Multiple races

9 (75)

3 (25)

 

0 (0)

1 (100)

 

1 (100)

0 (0)

 

  Unknown/refused

55 (80)

14 (20)

 

6 (55)

5 (45)

 

38 (78)

11 (22)

 

 Hispanic ethnicity

  

<0.0001

  

0.06a

  

0.13

  No

1337 (90)

154 (10)

 

243 (85)

44 (15)

 

530 (88)

70 (12)

 

  Yes

83 (77)

25 (23)

 

9 (64)

5 (36)

 

54 (82)

12 (18)

 

  Unknown/refused

3 (43)

4 (57)

 

0

0

 

0

0

 

 Marital status

  

0.001

  

0.04

  

0.04

  Married/cohabitating

1232 (90)

140 (10)

 

182 (87)

28 (13)

 

421 (89)

50 (11)

 

  Single

191 (82)

41 (18)

 

70 (77)

21 (23)

 

162 (84)

32 (16)

 

  Unknown/refused

0

2 (100)

 

0

0

 

1 (100)

0

 

 Education

  

<0.0001

  

0.07

  

0.03

  Did not graduate high school

63 (71)

26 (29)

 

16 (70)

7 (30)

 

46 (78)

13 (22)

 

  Graduated high school

196 (90)

21 (9.7)

 

41 (79)

11 (21)

 

83 (85)

15 (15)

 

  Any college education

1164 (90)

135 (10)

 

195 (86)

31 (14)

 

455 (89)

54 (11)

 

HEALTH-RELATED FACTORS

 Smoking status

  

0.40

  

0.06

  

0.46

  Never

664 (89)

85 (11)

 

156 (88)

22 (12)

 

374 (89)

47 (11)

 

  Former

629 (89)

75 (11)

 

71 (80)

18 (20)

 

150 (85)

26 (15)

 

  Current

130 (86)

22 (14)

 

25 (74)

9 (26)

 

60 (87)

9 (13)

 

  Unknown/refused

0

1 (100)

 

0

0

 

0

0

 

 Alcohol use

  

0.96

  

0.32

  

0.10

  None

341 (90)

39 (10)

 

116 (81)

27 (19)

 

233 (85)

40 (15)

 

  ≤1 drink/day

519 (90)

56 (9.7)

 

91 (88)

13 (12)

 

244 (91)

24 (9.0)

 

  >1 drink/day

453 (90)

51 (10)

 

26 (79)

7 (21)

 

71 (86)

12 (14)

 

  Unknown/refused

110 (75)

37 (25)

 

19 (90)

2 (9.5)

 

36 (86)

6 (14)

 

 Activity level

  

0.96

  

0.72

  

0.66

  Low

318 (89)

41 (11)

 

63 (81)

15 (19)

 

152 (87)

23 (13)

 

  Moderate

424 (89)

52 (11)

 

86 (84)

17 (16)

 

202 (87)

29 (13)

 

  High

665 (89)

86 (11)

 

98 (85)

17 (15)

 

222 (90)

26 (10)

 

  missing

16 (80)

4 (20)

 

5 (100)

0

 

8 (67)

4 (33)

 

 Taking a multivitamin

  

0.04

  

0.59

  

0.001

  No

650 (87)

97 (13)

 

149 (83)

31 (17)

 

191 (82)

42 (18)

 

  Yes

771 (90)

83 (9.7)

 

103 (85)

18 (15)

 

393 (91)

38 (8.8)

 

  Unknown/refused

2 (40)

3 (60)

 

0

0

 

0

2 (100)

 

 Taking calcium supplement

  

0.06

  

0.10

  

0.001

  No

1321 (88)

174 (12)

 

221 (82)

47 (18)

 

273 (84)

53 (16)

 

  Yes

100 (94)

6 (5.7)

 

30 (94)

2 (6.3)

 

310 (92)

27 (8.0)

 

  Unknown/refused

2 (40)

3 (60)

 

1 (100)

0

 

1 (33)

2 (67)

 

 Taking vitamin D supplement

  

0.04

  

0.39a

  

0.0001

  No

1360 (88)

178 (12)

 

229 (83)

47 (17)

 

370 (84)

68 (16)

 

  Yes

61 (97)

2 (3.2)

 

21 (91)

2 (8.7)

 

213 (95)

12 (5.3)

 

  Unknown/refused

2 (40)

3 (60)

 

2 (100)

0

 

1 (33)

2 (67)

 

 Number of prescription medications

 

0.27

  

0.02

  

0.77

  0

307 (86)

50 (14)

 

29 (78)

8 (22)

 

84 (87)

13 (13)

 

  1

360 (90)

38 (9.6)

 

59 (89)

7 (11)

 

145 (90)

16 (10)

 

  2

273 (88)

36 (12)

 

51 (94)

3 (5.6)

 

114 (87)

17 (13)

 

  3+

483 (89)

59 (11)

 

113 (78)

31 (22)

 

241 (87)

36 (13)

 

 Experienced chronic fatigue in last year

 

0.66

  

0.41a

  

0.11

  None

1357 (89)

171 (11)

 

219 (83)

44 (17)

 

531 (89)

69 (11)

 

  Some

51 (85)

9 (15)

 

23 (92)

2 (8.0)

 

40 (78)

11 (22)

 

  Severe

15 (88)

2 (12)

 

10 (77)

3 (23)

 

13 (87)

2 (13)

 

  Don’t know

0

1 (100)

 

0

0

 

0

0

 

 Experienced muscular pain in last year

 

0.53

  

0.05

  

0.33

  None

1228 (89)

154 (11)

 

210 (83)

43 (17)

 

488 (89)

63 (11)

 

  Some

171 (88)

23 (12)

 

38 (93)

3 (7.3)

 

76 (85)

13 (15)

 

  Severe

23 (82)

5 (18)

 

4 (57)

3 (43)

 

20 (80)

5 (20)

 

  Don’t know

1 (50)

1 (50)

 

0

0

 

0

1 (100)

 

 Experienced muscular weakness in last year

 

0.09

  

0.03a

  

0.31

  None

1358 (89)

167 (11)

 

234 (83)

47 (17)

 

534 (88)

72 (12)

 

  Some

54 (82)

12 (18)

 

16 (100)

0

 

38 (81)

9 (19)

 

  Severe

11 (79)

3 (21)

 

2 (50)

2 (50)

 

11 (92)

1 (8.3)

 

  Don’t know

0

1 (100)

 

0

0

 

1 (100)

0

 

 Experienced bone aches or pains in last year

 

0.11

  

0.42

  

0.56

  None

1215 (89)

151 (11)

 

208 (85)

37 (15)

 

455 (88)

63 (12)

 

  Some

170 (89)

21 (11)

 

30 (77)

9 (23)

 

96 (89)

12 (11)

 

  Severe

38 (79)

10 (21)

 

14 (88)

2 (12)

 

33 (83)

7 (17)

 

  Don’t know

0

1 (100)

 

0

1 (100)

 

0

0

 

 SF-36 mental component summary measure, mean (SD)b

55.9 (6.0)

55.0 (7.3)

0.09

53.9 (7.5)

53.0 (10.4)

0.58

54.2 (6.9)

51.8 (8.0)

0.01

 SF-36 physical component summary measure, mean (SD)b

53.9 (6.1)

53.1 (7.5)

0.65

53.5 (6.8)

51.7 (7.5)

0.12

52.8 (6.8)

49.3 (8.9)

0.0004

ADENOMA-RELATED FACTORS

 Number of baseline adenomas

  

0.29

  

0.53

  

0.48

  0

5 (83)

1 (17)

 

0

0

 

0

1 (100)

 

  1

916 (88)

128 (12)

 

190 (83)

39 (17)

 

453 (88)

60 (12)

 

  2+

502 (90)

54 (9.7)

 

62 (86)

10 (14)

 

131 (86)

21 (14)

 

 Baseline advanced adenomas

  

0.73

  

0.98

  

0.12

  No

1139 (89)

147 (11)

 

201 (84)

39 (16)

 

476 (87)

73 (13)

 

  Yes

253 (88)

35 (12)

 

51 (84)

10 (16)

 

103 (92)

9 (8.0)

 

  Unknown

31 (97)

1 (3.1)

 

0

0

 

5 (100)

0

 

 Family history of colorectal cancer

  

0.14

  

0.40

  

0.73

  No

1080 (88)

142 (12)

 

200 (84)

39 (16)

 

454 (88)

60 (12)

 

  Yes

238 (92)

22 (8.5)

 

39 (89)

5 (11)

 

95 (87)

14 (13)

 

  Unknown/refused

105 (85)

19 (15)

 

13 (72)

5 (28)

 

35 (81)

8 (19)

 

 Colonoscopy surveillance interval

  

0.73

  

0.12

  

0.003

  3 year

727 (88)

96 (12)

 

123 (87)

18 (13)

 

287 (92)

26 (8.3)

 

  5 year

696 (89)

87 (11)

 

129 (81)

31 (19)

 

297 (84)

56 (16)

 

STUDY-RELATED FACTORS

 Study center

  

<0.0001

  

0.33a

  

<0.0001

  A

227 (98)

5 (2.2)

 

29 (85)

5 (15)

 

86 (97)

3 (3.4)

 

  B

119 (97)

4 (3.3)

 

3 (100)

0

 

57 (95)

3 (5.0)

 

  C

75 (96)

3 (3.9)

 

16 (100)

0

 

45 (96)

2 (4.3)

 

  D

75 (90)

8 (9.6)

 

12 (92)

1 (7.7)

 

43 (96)

2 (4.4)

 

  E

242 (88)

33 (12)

 

59 (86)

10 (14)

 

64 (93)

5 (7.3)

 

  F

137 (87)

20 (13)

 

27 (87)

4 (13)

 

43 (66)

22 (34)

 

  G

143 (86)

23 (14)

 

32 (86)

5 (14)

 

62 (94)

4 (6.1)

 

  H

170 (85)

29 (15)

 

28 (80)

7 (20)

 

50 (82)

11 (18)

 

  I

123 (83)

25 (17)

 

31 (74)

11 (26)

 

73 (84)

14 (16)

 

  J

28 (80)

7 (20)

 

0

0

 

9 (82)

2 (18)

 

  K

84 (76)

26 (24)

 

15 (71)

6 (29)

 

52 (79)

14 (21)

 

 Taking prescription drug that requires staggered administration with study tablets

  

0.10

  

0.13

  

0.21

  No

1310 (89)

162 (11)

 

204 (85)

35 (15)

 

472 (87)

71 (13)

 

  Yes

113 (84)

21 (16)

 

48 (77)

14 (23)

 

112 (91)

11 (8.9)

 

 Counseled at baseline to change diet

  

0.57

  

0.13a

  

0.09a

  No

1381 (89)

178 (11)

 

250 (84)

47 (16)

 

578 (88)

78 (12)

 

  Yes

42 (91)

4 (8.7)

 

2 (50)

2 (50)

 

6 (67)

3 (33)

 

  Unknown

0

1 (100)

 

0

0

 

0

1 (100)

 

 Refused any questions during enrollment in-person questionnairec,d

  

0.01a

  

1.00a

  

0.01a

  No

1419 (89)

179 (11)

 

251 (84)

49 (16)

 

583 (88)

79 (12)

 

  Yes

4 (50)

4 (50)

 

1 (100)

0

 

1 (25)

3 (75)

 

 Answered ”Don’t know” to any questions during enrollment in-person questionnairec,d

  

0.01

  

0.59a

  

0.05

  No

1314 (89)

159 (11)

 

231 (84)

44 (16)

 

521 (89)

67 (11)

 

  Yes

109 (82)

24 (18)

 

21 (81)

5 (19)

 

63 (81)

15 (19)

 

 Refused any questions during enrollment self-administered questionnairesc

  

<0.0001

  

0.02

  

0.001

  No

1084 (91)

103 (8.7)

 

225 (86)

38 (14)

 

517 (89)

62 (11)

 

  Yes

339 (81)

80 (19)

 

27 (71)

11 (29)

 

67 (77)

20 (23)

 

 Scheduled next interview during enrollmentc

  

0.001

  

0.25

  

0.29

  No

261 (83)

52 (17)

 

44 (79)

12 (21)

 

113 (85)

20 (15)

 

  Yes

1162 (90)

131 (10)

 

208 (85)

37 (15)

 

471 (88)

62 (12)

 

 Number of enrollments conducted by coordinatorc

  

0.42

  

0.31

  

0.76

  1–10

16 (80)

4 (20)

 

6 (100)

0

 

17 (94)

1 (5.6)

 

  11–50

170 (86)

27 (14)

 

28 (82)

6 (18)

 

86 (87)

13 (13)

 

  51–100

364 (89)

46 (11)

 

77 (89)

10 (11)

 

132 (86)

21 (14)

 

  >100

873 (89)

106 (11)

 

141 (81)

33 (19)

 

349 (88)

47 (12)

 

 Coordinator worked in a prior polyp prevention trialc

  

0.01

  

0.48

  

0.49

  No

1034 (87)

144 (13)

 

211 (84)

39 (16)

 

413 (87)

61 (13)

 

  Yes

389 (92)

34 (8.0)

 

41 (80)

10 (20)

 

171 (89)

21 (11)

 
  1. Missing data are shown where values are not zero. p values are based on non-missing data, except for race
  2. aFisher exact test
  3. bp value from Kruskal-Wallis test because SF-36 scores are skewed
  4. cNot a priori potential predictors
  5. dExcludes questions asked as part of a skip pattern (N = 43 questions for men and 47 questions for women) and questions about beliefs in which “Don’t know” was an allowable response