Table 3.
Analysis of relation between journal impact factor, citation index factor, study sample size, publication delay, methodological quality, take home message content, concordance, and source of funding
| Is there a relation between: | Statistical tests* | Interpretation | Sensitivity analysis carried out? | If yes, what were results? |
|---|---|---|---|---|
| Methodological quality and JIF (with aggregate moderate and high risk of bias studies)? | z=1.3, P=0.184 | No evidence of difference in mean JIF between studies with low risk of bias and studies with (high or moderate) risk of bias | No | — |
| Methodological quality and CIF (with aggregate moderate and high risk of bias studies)? | z=−0.19, P=0.851 | No evidence of difference in mean CIF between studies with low risk of bias and studies with (high or moderate) risk of bias | No | — |
| Methodological quality and CSS (with aggregate moderate and high risk of bias studies)? | z=−0.96, P=0.338 | No evidence of difference in mean CSS between studies with low risk of bias and studies with (high or moderate) risk of bias | Yes (only with RCT) | No change in interpretation |
| Methodological quality and PD (with aggregate moderate and high risk of bias studies)? | z=−0.38, P=0.707 | No evidence of difference in mean PD between studies with low risk of bias and studies with (high or moderate) risk of bias | No | — |
| Take home message and JIF? | z=−1.51, P=0.131 | No evidence of difference in mean JIF between studies with favourable take home message and studies with mixed/unfavourable take home message | No | — |
| Take home message and CIF? | z=−1.84, P=0.065 | No evidence of difference in mean CIF between studies with favourable take home message and studies with mixed/unfavourable take home message | No | — |
| Take home message and CSS? | z=−0.41, P=0.682 | No evidence of difference in mean CSS between studies with favourable take home message and studies with mixed/unfavourable take home message | Yes (only with RCT) | No change in interpretation |
| Take home message and PD? | z=−0.89 P=0.375 | No evidence of difference in mean PD between studies with favourable take home message and studies with mixed/unfavourable take home message | No | — |
| Concordance between data presented and conclusions reported and JIF? | z=1.1, P=0.273 | No evidence of difference in mean JIF between studies with concordance (yes) and studies with concordance (no/part/unclear) | No | — |
| Concordance between data presented and conclusions reported and CIF? | z=0.35 P=0.729 | No evidence of difference in mean CIF between studies with concordance (yes) and studies with concordance (no/part/unclear) | No | — |
| Concordance between data presented and conclusions reported and CSS? | z=0.84, P=0.404 | No evidence of difference in mean CSS between studies with concordance (yes) and studies with concordance (no/part/unclear) | Yes (only with RCT) | No change in interpretation |
| Concordance between data presented and conclusions reported and PD? | z=−0.58, P=0.563 | No evidence of difference in mean PD between studies with concordance (yes) and studies with concordance (no/part/unclear) | — | — |
| Funding source and JIF? | χ2=27.4, df=2, P<0.001 | Evidence of difference in mean JIF between studies with industry funding source and other funding source. Mean JIF significantly greater in industry funded studies than studies with other funding source | Excluding studies with undeclared funding | No change in interpretation |
| Funding source and CIF? | χ2=13.5, df=2, P<0.001 | Evidence of difference in mean CIF between studies with industry funding source and other funding source. Mean CIF significantly greater in industry funded studies than studies with other funding source | Excluding studies with undeclared funding | Change in interpretation: “no evidence” |
| Funding source and CSS? | χ2=0.06, df=2, P=0.997 | No evidence of difference in mean CSS between industry funded studies and government funded studies | Excluding studies with undeclared funding and only with RCT | No change in interpretation |
| Funding source and PD? | χ2=0.97, df=2, P=0.616 | No evidence of difference in mean PD between industry funded studies and government funded studies | Excluding studies with undeclared funding | No change in interpretation |
JIF=journal impact factor; CIF=citation index factor; RCT=randomised controlled trial; CSS=comparator sample size; PD=publication delay (difference between publication year and end of study).
*Kruskal Wallis (χ2) or Wilcoxon (z).