Systematic review.

A structured review that gathers and appraises all relevant studies.

A systematic review uses an explicit, pre-specified, reproducible method to find, appraise, and synthesize every study relevant to a defined question. The protocol is normally registered before the work starts, the search strategy and databases are stated so anyone can repeat them, inclusion and exclusion criteria are fixed in advance, and the quality of each included study is assessed rather than assumed. The point of all that machinery is to remove the reviewer's discretion about which studies to feature, which is what separates it from a narrative review where an author selects supporting examples. Systematic reviews may or may not include a meta-analysis; when the studies are too different to pool sensibly, a good review says so and synthesizes them descriptively instead. For anyone reading about peptides, this is the most useful document type to look for, because it tells you what the whole body of evidence looks like rather than what the most quotable single study found. The misunderstanding worth correcting is that any article surveying a topic is a systematic review. Review articles are common and often useful, but without a stated search method and appraisal step they carry the author's selection preferences along with their conclusions.