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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