I am performing a meta-analysis and my search was extended to EMBASE.
As part of the process I have retrieved a few abstracts that were included in some congress abstract books. The results of these congress communications are not yet published as full papers, but still some data is potentially extractable from these abstracts and could be included in the meta-analysis.
Should I include them and state it in the Materials and methods section?
I know that they have low quality evidence that could possibly bias the research but wouldn't it be worse to exclude something that could be counted?
Thank you very much for your suggestions!