https://academic.oup.com/bmb/article-pdf/121/1/19/13623695/ldw058.pdf

 

From: Evidence based health (EBH) [mailto:[log in to unmask]] On Behalf Of Tom Jefferson
Sent: Thursday, April 27, 2017 5:30 AM
To: [log in to unmask]
Subject: Re: Systematic reviews, what am I missing?

 

Norman, could you please send a pdf of the paper?

Thanks,

Tom.


Dr Tom Jefferson

Senior Associate Tutor

University of Oxford

Oxford OX2 6GG

 

On 27 April 2017 at 11:28, Norman Vetter <[log in to unmask]> wrote:

We have recently published a review on the ethics of reporting all the results of clinical trials:

 

https://academic.oup.com/bmb/article/121/1/19/2926156/The-ethics-of-reporting-all-the-results-of

 

Norman Vetter

 

On 27 April 2017 at 09:59, Jon Brassey <[log in to unmask]> wrote:

Stimulated by a recent paper on stem cells (http://www.cell.com/stem-cell-reports/pdf/S2213-6711%2817%2930119-4.pdf) reported that nearly half of stem cells trials aren't reported.  This falls in the range of OpenTrials which report 30-50% of trials aren't reported.  It got me thinking:

  • Many trials are unpublished.

Further. a couple of definitions of systematic reviews:

 

1) A Brief History of Research Synthesis EVALUATION & THE HEALTH PROFESSIONS, Vol. 25 No. 1, March 2002 12-37
SYSTEMATIC REVIEW The application of strategies that limit bias in the assembly, critical appraisal, and synthesis of all relevant studies on a specific topic. Meta-analysis may be, but is not necessarily, used as part of this process.

 

2) Cochrane's
A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making.

 

The first definition would suggest - as it states 'all relevant studies' - that most systematic reviews are not really systematic reviews as they miss lots of trials.

The second definition is more flexible by saying "..attempts to identify, appraise and synthesize...".  It's more flexible as it's not saying 'all' merely that you 'attempt' to identify all the evidence. 

 

So, two questions to the group:

 

  • Based on the first definition, are systematic reviews that don't include 'all relevant studies' not actually systematic reviews?
  • Based on the second definition, any clue as to how hard one should 'attempt' to locate all the evidence?  For instance, systematic reviews tend to try to locate ALL published journal articles and - generally - a fairly poor attempt at unpublished trials, who decided that and is it evidence based?

I look forward to hearing from you all.

 

Best wishes

 

jon

 

--

 

Jon Brassey

Director, Trip Database

Honorary Fellow at CEBM, University of Oxford

 



 

--

Norman Vetter
Web page: www.normanvetter.com