Non-Cochrane vs. Cochrane reviews were twice as likely to have positive conclusion statements: cross-sectional study.
OBJECTIVE
To determine which factors predict favorable results and positive conclusions in systematic reviews (SRs) and to assess the level of agreement between SR results and conclusions.


METHODS
A sample of 296 English SRs indexed in MEDLINE (November, 2004) was obtained. Two investigators independently categorized SR characteristics, results, and conclusions. Descriptive analyses and logistic regression predicting favorable results (nonstatistically significant and statistically significant positive) and positive conclusions were conducted. The level of concordance between results and conclusions was assessed using a weighted-kappa statistic.


RESULTS
Overall, 36.5% of the SRs had favorable results, increasing to 57.7% for Cochrane and 64.3% for non-Cochrane reviews with a meta-analysis of the primary outcome. Non-Cochrane reviews with a meta-analysis of the primary outcome were twice as likely to have positive conclusions as Cochrane reviews with such an analysis (P-value<0.05). The weighted kappa for agreement between SR results and conclusions was 0.55. It was lower for Cochrane (0.41) vs. non-Cochrane (0.67) reviews.


CONCLUSIONS
SRs including a meta-analysis of the primary outcome may be affected by indirect publication bias in our sample. Differences between the results and conclusions of Cochrane and non-Cochrane reviews were apparent. Further research on publication-related issues of SRs is warranted.
Tricco
Andrea C
AC
Chalmers Research Group, Children's Hospital of Eastern Ontario Research Institute, 401 Smyth Road, Ottawa, Ontario, Canada.
Tetzlaff
Jennifer
J
Pham
Ba'
B
Brehaut
Jamie
J
Moher
David
D
D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D015201:Meta-Analysis as Topic; D015588:Observer Variation; D017594:Publication Bias; D015203:Reproducibility of Results; D012196:Review Literature as Topic