Hi Venu Chippa

This was answered in detail previously in this thread

https://www.researchgate.net/post/Can-we-include-case-studies-and-experimental-studies-together-for-systematic-review

You can use case report, case series or case control study but should on same topic . and level of evidence will be weak but We use RCT for systemic Review quality of evidence will be strong . Definitely we can for systemic Review

We cannot use it since we compare apples with apples (most likely we compare things with similar standards or bases). Hence, evidence obtained from case reports may not be compatible with evidence obtained using case-control studies.

Definitely but case report or case series systemic review having lesse quality than RCT