Find out if your topic has already had a Systematic Review(SR) conducted on it.
If so, stop and analyze the review with these questions:
1. Was it conducted using the rigor and methodologies available through Joanna Briggs Institute, Cochrane Systematic Reviews Database, Campbell's Collaboration of Systematic Reviews, John Hopkins (published in Cochrane)? If not then it might not be a true Systematic Review.
2. How old is the document? If 10 years or older than sometimes there is need for a new review. Ensure there have been no updates to the document already made. It is also courteous to contact the author and see if they have any interest in updating.
3. Is it truly your topic? Sometimes the SR might look like your topic initially, but upon further inspection the SR is looking at something just a bit different from your own. For example they be looking at a different scale or measurement than you are.
If the SR does match your idea, than you could change your topic just a bit, so that you are looking at something else. For example you could change your population, an example could be you wanted to look at a population of adults, but now you want to conduct your SR on pediatrics.