Hey Teshome,

I know this problem. In case there are really no single studies for your question out there, I see two options. 1) Broaden your research questions or 2) choose another methodological approach. If your questions has never been pursued by others a systematic review does not make sense. In this case, an empirical study is necessary.

But I would really get sure that you have not missed relevant studies. I would recheck your search strategy (terms, databases, etc.) for your literatur search.

Best regards to Addis...the home town of my father in law...maybe we meet up one time :-)

Best regards from Germany,

Christian

Hi Teshome

I agree with Christian that perhaps your research question and eligibility criteria are too narrow and maybe a different methodology is needed.

Generally, results are what they are. If everything is correct, maybe there are valid reasons you did not find trials (new interventions, rare diseases or maybe research priorities do not coincide with those of pharmacy, healthcare decision makers...or who knows what other reasons are out there). Certainly, you should justify the fact the review is empty and why there is the need to start filling it...so that you can stimulate research (and of course you run the risk that there is no such need)

Empty reviews is a common problem in the Cochrane library with hundreds of published empty reviews. I once asked some editors how is it possible that there is a need for a systematic review when noone has thought of the need for a trial. The answer, more or less, was that you set the review question and then it is populated with time (typically it is advised that a review should be updated every two years). This makes some sense but then I had a look at the Cochrane library and saw empty reviews that have never been updated, even after many years. I randomly looked at 3-4 empty reviews and none was updated. I then stopped cause I had taken the answers I was looking for.

The reccomendation of an empty review is a statement that more research is needed (not very fancy). You do not have evidence from the included studies. Maybe you can use evidence from the excluded studies but there are valid reasons you excluded them. Then you will have to approach your research question using another methodology

In a nutshell, there is not a problem and it is quite common to have an empty review. On the other hand, you do not have evidence from the systematic review to provide conclusions (and you say the review is important for future direction)

Best wishes

Dimitris

I agree with Christian Ghanem

You should ultimately broaden the research questions. You can try both human and animal studies. In case only human, then you can add both randomized and non-randomized studies. You also try case-control, case series studies.

I am little confused about your search strategy. At first, develop your search strategy by only using population and intervention. Next, find out relevant studies from grey literature databases.

Thank you.

Thank you please

Refer the document of Introduction to systematic review

and meta-analysis

If you follow systematic review methodology rigorously and your current question is very much relevant, you can do a systematic review. If your review will not find any study that will also be a finding that an primary study is needed on the topic. I am agree with Christian Ghanem, you can think of broaden of your research question, if it's feasible.