Two reviews can discuss the same peptide and reach different conclusions because they asked different questions or selected different evidence. Before comparing their conclusions, examine how each assembled its literature. A polished explanation and a long reference list do not, by themselves, reveal that process.
Identify the job the review is doing
A review may explain the history of a concept, propose a mechanism or answer a tightly defined question about an effect. These jobs require different kinds of organisation. A historical overview need not be mistaken for a complete assessment of every experiment.
Cochrane defines systematic reviews around a specified question, explicit eligibility criteria and methods intended to reduce bias when identifying and evaluating relevant evidence. The goal is a transparent attempt to assemble the eligible evidence, rather than an assurance that nothing was missed.Cochrane Handbook — Chapter 1: Starting a review (opens in a new tab)
For a narrative account, look for an explanation of why the cited papers were chosen and what territory the author intends to cover. Without that information, it can still introduce useful ideas, but its omissions are difficult to evaluate.
Our educational Research Hub guides are authored explanations with linked sources. They should not be read as formal systematic reviews merely because they discuss research or provide references.
Ask how a paper entered the review
| Question | Why it matters |
|---|---|
| What was eligible? | Defines the evidence the conclusion concerns |
| Where was it sought? | Makes the search coverage inspectable |
| When was it searched? | Sets the last evidence date |
| Why was it excluded? | Reveals the boundary around the included set |
Consider an original hypothetical review of Peptide R. It cites six favourable experiments but does not state whether unfavourable experiments were eligible. You cannot tell from the six citations whether they represent the available research or the examples selected for the argument.
A second review explicitly limits itself to receptor-binding experiments. Its omission of animal studies may be appropriate for that question. The same omission would matter if its conclusion claimed to cover all biological effects.
The issue is therefore not simply how many papers appear. It is whether the route from the question to the included set can be followed and whether the conclusion stays within that set’s scope.
Separate selection from the way results are presented
A review can describe results in prose and tables without calculating a pooled estimate. That presentation choice does not tell you whether its evidence was selected systematically. Conversely, the presence of a combined number does not establish a complete or unbiased search.
When a paper calls itself a meta-analysis, inspect both layers: how the studies were found and whether combining their estimates answers a meaningful question. A sophisticated calculation cannot recover relevant studies that were excluded for unjustified reasons.
Also distinguish the review’s conclusion from the included studies’ conclusions. An author may offer a new interpretation across papers; that interpretation should remain identifiable rather than appearing to be a finding directly measured in each experiment.
Use each review at the level it supports
A broad explanatory review can help you learn vocabulary and locate influential papers. A focused evidence synthesis may be more useful for checking how consistently a defined comparison has been studied. Neither use makes the review a substitute for checking a pivotal original result.
Record the search or coverage date separately from the publication date. A recently published review may have searched substantially earlier, and a current-looking webpage may reproduce an older account.
When reviews disagree, compare their questions, eligibility boundaries and included studies before assuming that one author misread the science. A disagreement about different evidence sets may not be a disagreement about the same proposition.
Sources and further detail
- Cochrane Handbook — Chapter 1: Starting a review (opens in a new tab)
Sections 1.1–1.5 read for explicit review questions, eligibility and methods. The review-comparison examples and reading workflow are original; this guide is not a formal systematic review.
Sources checked 19 September 2026. Worked examples are illustrative unless a supplied report is explicitly identified. This article has not undergone independent scientific peer review.