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Table 2 Comparison of mean of PRISMA for abstracts items reported in abstracts of meta-analyses of RCT

From: A comparison of quality of abstracts of systematic reviews including meta-analysis of randomized controlled trials in high-impact general medicine journals before and after the publication of PRISMA extension for abstracts: a systematic review and meta-analysis

Variables

N

Univariable analysisa

Multivariable analysisb

Means (standard deviation)

Mean difference (95 % CI)

p value

Adjusted means (95 % CI)

Adjusted mean difference (95 % CI)

p value

Year

 - 2012 (ref)

84

6.7 (1.6)

  

7.0 (6.5; 7.5)

 

<0.001*

 - 2014

59

6.8 (1.6)

0.1 (−0.4; 0.7)

0.694

6.9 (6.4; 7.4)

−0.1 (−0.6; 0.4)

0.711**

 - 2015

61

7.5 (1.6)

0.8 (0.2; 1.3)

0.007

7.8 (7.4; 8.3)

0.9 (0.4; 1.3)

0.001***

Abstract word count

 - <300 (ref)

30

8.3 (2.0)

  

6.9 (6.3; 7.4)

  

 - ≥300

113

6.7 (1.4)

−0.3 (−1.3; −1.0)

<0.001

7.6 (6.8; 8.4)

0.7 (−0.4; 1.8)

0.184

PRISMA endorsement

 - Non endorser journals (ref)

43

7.9 (1.9)

  

7.7 (7.1; 8.2)

  

 - Endorser journals

100

6.6 (1.4)

−1.3 (−1.9; −0.7)

<0.001

6.8 (6.2; 7.4)

−0.8 (−1.7; 0.04)

0.063

Abstract format

 - IMRAD (ref)

47

6.4 (1.6)

  

6.9 (6.3; 7.4)

  

 - 8-headings

96

7.3 (1.6)

0.8 (0.4; 1.3)

<0.001

7.6 (7.2; 8.0)

0.7 (0.2; 1.2)

0.008

Publication on behalf of a group

 - No (ref)

131

7.0 (1.7)

  

7.3 (7.0; 7.7)

  

 - Yes

12

6.7 (1.4)

−0.3 (−1.1; 0.4)

0.394

7.1 (6.5; 7.8)

−0.2 (−0.8; 0.5)

0.557

Number of authors

 - ≤6 (ref)

64

6.9 (1.6)

0.1 (−0.4; 0.6)

0.659

7.2 (6.7; 7.6)

  

 - >6

79

7.0 (1.7)

  

7.3 (6.9; 7.7)

0.2 (−0.3; 0.6)

0.464

  1. Ref reference for mean difference calculation, PRISMA preferred reporting items for systematic review and meta-analysis, IMRAD introduction, methods, results, and discussion
  2. aStudent’s t test, *Global p value
  3. bGeneralized estimation equations with journals as grouping variable. Goodness of Fit: value of the Corrected Quasi-likelihood under Independence Model Criterion = 1827.12 and the value of the Quasi-likelihood under Independence Model Criterion = 1829.28
  4. After Bonferroni correction for multiple comparisons, values are **1.0 and *** 0.002