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Table 5 Post-hoc comparison of reporting in publications, and changes in reporting from abstract to publication, according to journal impact factor

From: Publication bias in animal research presented at the 2008 Society of Critical Care Medicine Conference

Variable Prevalence in lower impact n = 32 Prevalence in higher impact n = 30 p value of comparison Change from abstract (A) to publication (P)
Randomized 12 (38%) 12 (40%) 0.99  
 Change from A to P 8 (25%) 4 (13%) 0.25 All 12: from non-R in A, to R in P
 Method 0 (0%) 0 (0%)
 Allocation concealment 0 (0%) 0 (0%)
Blinding (possible) 0 (0%) 4 (13%) 0.049  
 Change from A to P 0 (0%) 4 (13%) 0.049 All 4: from no mention in A, to blinding of some outcomes in P
Sample size calculation 0 (0%) 0 (0%)
Primary outcome stated 3 (9%) 0 (0%) 0.09  
 Change from A to P 3 (9%) 6 (20%) 0.24 All 9: state in A, to not stated in P
Numbers with denominators 8 (25%) 13 (43%) 0.13  
 Change from A to P 6 (19%) 10 (33%) 0.19 All 16: no denominators in A, to denominators in P
Main outcomes positive 32 (100%) 30 (100%)  
 Change from A to P 4 (13%) 1 (3%) 0.19 All 5: negative in A, to positive or excluded in P
Number of animals stateda 17 (53%) 18 (60%) 0.59  
 Change from A to P 6 (19%) 7 (23%) 0.66 From A to P the number was smaller in 3 (9%) and larger in 10 (29%)a
Statistically significant result of main outcomes 30 (94%) 28 (93%) 0.95  
 Change from A to P 13 (41%) 10 (33%) 0.55 All 23: not significant (or not stated) in A, to significant in Pb
Months to publication 27 (SD 17) 18 (SD 16) 0.02
  1. Comparisons made using Fisher’s Exact or Chi square test, or independent samples student t test, as appropriate
  2. A abstract, P publication, R randomized
  3. a In the 13 that changed in animal numbers from A to P: in the lower and higher impact P the number was smaller in 1 (by n = 4) and 2 (by n = 3 and 6), and larger in 5 (by n = 4, 14, 36, 52, 54) and 5 (by n = 4, 5, 7, 22, 25) respectively
  4. b In the 23 that changed in statistical significance from A to P, in the lower and higher impact P respectively: the animal numbers did not change in 4 and 1 (p = 0.19) [these numbers did change in 2 and 2 (larger number in 2, and smaller number in 2), and change could not be determined in the rest because numbers were not stated in P in 6 and 3, and were not stated in the A in 1 and 4]; the main outcomes changed in 2 and 0 (p = 0.16); and denominators changed in 1 and 2 (p = 0.52) [change could not be determined in 19 others because denominators were not reported in 11 and 8; thus we could be sure that denominators did not change in 1]