A systematic review of literature adopts

A systematic review adopts explicit, pre-specified procedures so the whole process is transparent and reproducible.

It states clear inclusion and exclusion criteria and a documented search strategy before studies are gathered.

Implicit procedures describe the traditional narrative review, which relies on the reviewer's undisclosed judgement.

Personal choice procedures would introduce bias and defeat the aim of an unbiased evidence synthesis.

Peer suggested procedures rest on informal advice rather than a written, replicable protocol.

This explicitness lets another reviewer repeat the search and reach comparable conclusions.