To avoid duplication, you should check for existing evidence synthesis reviews on your topic. You can do this by searching literature databases, such as PubMed, using terms for your topic combined with terms for review type you are seeking to complete:

Example: topic AND ("systematic review" OR "Scoping review" OR "rapid review" OR "evidence synthesis" OR "knowledge synthesis" OR "umbrella review")

The following resources are also good places to check for existing reports:

JBI Evidence Based Practice database - includes all types of evidence synthesis (systematic reviews, scoping reviews, etc..)

The Cochrane Database of Systematic Reviews - systematic reviews

PROSPERO - protocols of systematic reviews