Searching for unpublished trials in Cochrane reviews may not be worth the effort
- PMID: 19128939
- DOI: 10.1016/j.jclinepi.2008.09.010
Searching for unpublished trials in Cochrane reviews may not be worth the effort
Abstract
Objective: To assess the value of searching for unpublished data by exploring the extent to which Cochrane reviews include unpublished data and by evaluating the quality of unpublished trials.
Study design and setting: We screened all 2,462 completed Cochrane reviews published since 2000 in the Cochrane Database of Systematic Reviews Issue 3, 2006. In a random sample (n=61) of 292 reviews, including unpublished trials, we studied all 116 references.
Results: Unpublished trials make up 8.8% of all included trials in our sample. Thirty-eight percent of the "unpublished" trials have in fact been published. Allocation concealment was "unclear" or not adequate in 54.3% and 61.3% reported blinding. In 47.2% reported withdrawal rates were >20%. Trials that were eventually published had larger mean population sizes (P-value, 0.02). Of the reported sponsors, 87.3% were drug companies. Methodological quality and publication bias are mentioned in half of the reviews and explored in a third. Quality ratings did not have consequences for pooling, because 82.8% was included in the forest plots.
Conclusions: A minority of Cochrane reviews include "unpublished trials" and many of these are eventually published. Truly unpublished studies have poor or unclear methodological quality. Therefore, it may be better to invest in regular updating of reviews, rather than in extensive searching for unpublished data.
Similar articles
-
Cochrane reviews used more rigorous methods than non-Cochrane reviews: survey of systematic reviews in physiotherapy.J Clin Epidemiol. 2009 Oct;62(10):1021-30. doi: 10.1016/j.jclinepi.2008.09.018. Epub 2009 Mar 17. J Clin Epidemiol. 2009. PMID: 19282144 Review.
-
The quality of reports of critical care meta-analyses in the Cochrane Database of Systematic Reviews: an independent appraisal.Crit Care Med. 2007 Feb;35(2):589-94. doi: 10.1097/01.CCM.0000253394.15628.FD. Crit Care Med. 2007. PMID: 17205029
-
Reporting of adverse events in systematic reviews can be improved: survey results.J Clin Epidemiol. 2008 Jun;61(6):597-602. doi: 10.1016/j.jclinepi.2007.10.005. Epub 2008 Apr 14. J Clin Epidemiol. 2008. PMID: 18411039
-
An international survey indicated that unpublished systematic reviews exist.J Clin Epidemiol. 2009 Jun;62(6):617-623.e5. doi: 10.1016/j.jclinepi.2008.09.014. Epub 2009 Jan 21. J Clin Epidemiol. 2009. PMID: 19162440
-
[Systematic reviews on infectious diseases. The Cochrane Collaboration].Enferm Infecc Microbiol Clin. 1999;17 Suppl 2:15-21. Enferm Infecc Microbiol Clin. 1999. PMID: 10605185 Review. Spanish.
Cited by
-
Different antibiotic treatments for group A streptococcal pharyngitis.Cochrane Database Syst Rev. 2016 Sep 11;9(9):CD004406. doi: 10.1002/14651858.CD004406.pub4. Cochrane Database Syst Rev. 2016. Update in: Cochrane Database Syst Rev. 2021 Mar 17;3:CD004406. doi: 10.1002/14651858.CD004406.pub5. PMID: 27614728 Free PMC article. Updated. Review.
-
How should systematic reviewers handle conference abstracts? A view from the trenches.Syst Rev. 2019 Nov 7;8(1):264. doi: 10.1186/s13643-019-1188-0. Syst Rev. 2019. PMID: 31699124 Free PMC article.
-
Association Between Shame and Posttraumatic Stress Disorder: A Meta-Analysis.J Trauma Stress. 2019 Aug;32(4):484-495. doi: 10.1002/jts.22411. Epub 2019 Jul 10. J Trauma Stress. 2019. PMID: 31291483 Free PMC article.
-
Defining the process to literature searching in systematic reviews: a literature review of guidance and supporting studies.BMC Med Res Methodol. 2018 Aug 14;18(1):85. doi: 10.1186/s12874-018-0545-3. BMC Med Res Methodol. 2018. PMID: 30107788 Free PMC article. Review.
-
Impact of heat stress on the reproductive performance and physiology of ewes: a systematic review and meta-analyses.Int J Biometeorol. 2019 Jul;63(7):949-962. doi: 10.1007/s00484-019-01707-z. Epub 2019 Mar 19. Int J Biometeorol. 2019. PMID: 30888508
MeSH terms
LinkOut - more resources
Full Text Sources
