Hi
i am trying to conduct an umbrella review.
there are some systematic reviews that report the same outcome and have same included RCTs (not all of the RCTs are similar but some of them repeated in two same meta analysis). I can not delete any of the systematic reviews because they reported different studies as well ( it seems that it is because of using different data sources)
can i include all of the systematic review and meta analyses?
Hi Alireza Keshtkar,
From my personal perspective, if these systematic reviews contain the same articles but provide different results or contain different articles but measure the same results, this should be included within the umbrella review. Alireza Keshtkar
Hi Alireza,
The phenomenon you are describing is called "overlap". You can handle overlap at different stages of the umbrella review (or overview). You can define it as part of the eligibility criteria (e.g. not including a SR if it shares a certain amount of primary studies with another), at the moment of data extraction (e.g. in case of overlap, extracting data only from the most recent SR, or the one with the highest quality, etc), you can describe it within your results, or you can acknowledge that as a limitation. Carole Lunny has a great scoping review about this:
- 10.1186/s13643-017-0617-1
- 10.1186/s13643-018-0784-8
If you decide to describe the overlap as part of your results (the option I would recommend), I would suggest you do the following:
- Make a matrix of evidence to visualise overlap
- Calculate the corrected covered area to quantify the overall overlap (10.1016/j.jclinepi.2013.11.007)
- Calculate a pairwise corrected covered area (10.1002/jrsm.1588)
With that description, you can decide if it would be better to present your results descriptively, or maybe try to solve the overlap by conducting a de novo meta-analysis. Don't ever do a meta-meta-analysis!
I did a talk about this topic recently, here is the link: https://youtu.be/QDrbL3zxUrU?si=r0Er0vWI4QJMNyyk
Hope this helps!
Javier
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