Yes, a medical review can cite earlier reviews for context, but data should come from primary studies unless you’re writing an overview of reviews.
What Readers Want To Know Right Away
Writers face this knot often: many syntheses already exist, and you’re asking if those papers can sit inside your own medical evidence review. Yes for background, mapping, and methods leads; no for outcome data unless your project is an overview of reviews or umbrella review. That line keeps bias low and avoids counting the same trial twice.
Using Other Reviews Inside A Clinical Evidence Review: When It Works
Think of prior syntheses as signposts. They signal where trials cluster, which outcomes matter to clinicians, and which search terms pull the right records. You can mine their reference lists, note prior inclusion rules, and learn common risk-of-bias pitfalls. Then you still extract from the primary studies that meet your own criteria.
This approach fits narrative reviews, scoping reviews, rapid reviews, and full systematic reviews of interventions or diagnostics. In all of those, earlier syntheses help you frame the question and plan the search. They aren’t your data source unless your method states that you’re summarizing reviews rather than trials.
Why You Shouldn’t Lift Effect Sizes From Another Review
Pulling pooled estimates from a prior meta-analysis sounds quick. It also invites double counting, mismatched eligibility, and outdated decisions on model choice. One review might include quasi-randomized work you plan to exclude. Another might mix time points that you plan to separate. Extracting from the trials themselves keeps decisions under your control.
| Role | What You Can Do | What To Avoid |
|---|---|---|
| Background | Summarize themes and gaps in short text | Copying paragraphs or conclusions wholesale |
| Search Setup | Harvest terms and trial IDs from reference lists | Stopping after one review’s references |
| Screening | Use prior inclusion rules as a starting template | Adopting another team’s criteria without edits |
| Data Extraction | Extract from underlying trials you find | Reusing pooled effects from another review |
| Appraisal | Note common risks flagged by others | Letting their judgments replace your own |
| Reporting | Cite who did what and when | Vague mentions like “past studies show…” |
When A Review Of Reviews Is The Right Design
Sometimes the field already has dozens of systematic reviews, each covering a slice. In that case an overview of reviews (often called an umbrella review) can answer a top-level clinical question neatly. Your unit of analysis becomes the review, not the trial. You assess overlap across reviews, rate each review’s methods, and present the strength of evidence at the review level.
That design needs extra care for overlap, since the same trial may appear in several source reviews. Teams map overlap before any pooling, or they pre-select one review per outcome using transparent rules. Many groups also appraise source reviews with a structured tool and report how judgments fed into the summary.
Core Rules For Overviews And Umbrella Reviews
- Write a protocol, state outcomes, and pre-plan how you’ll handle overlap.
- Chart which primary studies appear in which source reviews.
- Use a review appraisal tool, and separate poor methods from sound ones.
- Explain if you will re-extract trial data or rely on the review’s tables.
Reporting And Transparency That Editors Expect
Editors and readers want clarity on why you cited other syntheses, how you found trials, and how you kept double counting at bay. Two simple anchors handle most of that need. First, follow the PRISMA 2020 reporting guideline for your flow diagram, tables, and wording. Second, if your design is an overview, read the Cochrane guidance on overviews of reviews for rules on overlap and selection.
Those sources set expectations for itemized search strategies, inclusion rules, and certainty ratings. They also push you to show who made each decision and which judgments were done in duplicate. That trail builds trust without bloating the manuscript.
Method Choices: Step-By-Step
Define The Review Type
Pick the design that matches your aim. Narrative pieces map the field and point to gaps. Scoping reviews show what evidence exists and where. Full systematic reviews answer a tightly framed question with pre-specified methods. Overviews synthesize reviews when trials are already well covered by prior syntheses.
Set Inclusion And Exclusion Rules
Write clear criteria before screening starts. State population, intervention, comparator, and outcomes. Add study design rules and minimum follow-up where it matters. If you plan an overview, define which types of reviews can enter and how you’ll rank them if several cover the same outcome.
Build And Pilot Searches
Design database strategies with synonyms, controlled vocabulary, and Boolean pairs. Pilot the string to see if it retrieves a known trial set. Save every line in a supplement. When you’re taking cues from prior syntheses, copy the terms into your notes and then extend them so the net reaches new trials and records beyond the earlier window.
Screen In Duplicate
Two people should screen titles, abstracts, and full text. Calibrate first on a small batch, then run the set. Record reasons for exclusion at the full-text stage. This step reduces missed trials and disagreements.
Extract From The Right Source
If your unit of analysis is a trial, pull numbers from the trial report or a registry record. If your unit is the review, pull from the review’s tables but capture its eligibility rules, date range, model, and risk-of-bias method. Note any mismatches between reviews on the same outcome.
Appraise With A Fit-For-Purpose Tool
Trial-level reviews use risk-of-bias tools that fit the study design. Review-level syntheses often add AMSTAR 2 to judge methods and reporting. The output isn’t a numeric score; it’s a pattern of strengths and weaknesses that feeds your certainty judgments.
Common Pitfalls And Clean Fixes
Double Counting The Same Trial
When you cite several syntheses, the same trial can slip in twice during data extraction. Fix that with a cross-walk list that links each trial ID to all reviews that included it. Use the list during meta-analysis to keep one line per trial.
Mismatched Eligibility And Outcomes
Prior syntheses may group outcomes your team plans to separate. They may allow designs or comparators you’re excluding. Read inclusion rules closely, and don’t inherit pooled numbers that conflict with your plan.
Out-Of-Date Searches
Many syntheses stop searching earlier than your window. Treat their reference lists as a springboard, not a ceiling. Run updated searches through the same databases plus any new ones that fit your topic.
Opaque Reporting
Readers need to see which steps used prior syntheses and which steps used trial reports. Label that in your methods and in your flow diagram. State how many records came from database searches, registries, and backward/forward citation chasing.
What To Cite And How To Word It
When a past synthesis helps shape your plan, cite it in the methods section. Use neutral wording: who did the work, what years, which designs, and which outcomes. When you find a trial through a review’s reference list, cite the trial, not the review, for any numbers you use. Reserve review-level citations for background text and for methods notes.
Language That Keeps Editors Happy
Stick to clear, testable claims. Avoid phrases that imply certainty without data. Name the design. Name the source for each set of numbers.
Quick Decision Grid
Use this snapshot to set your approach before you write a line.
| Task | Use Prior Reviews | Use Primary Studies |
|---|---|---|
| Topic Framing | Yes, for scope and themes | No data use |
| Search Terms | Yes, seed strings and trial IDs | Not needed |
| Study Selection | Template only | Yes, apply your rules |
| Risk Of Bias | Note patterns others saw | Judge each trial |
| Effect Estimates | Only in overviews | Yes, pull and pool |
| Certainty Rating | Only if rating reviews | Yes, rate outcomes |
| Conclusions | Context and gaps | Data-based statements |
Ethics, Credit, And Duplicate Work
Recycling text or numbers from another team’s synthesis crosses editorial lines. Journals expect you to cite the source review for ideas and to pull numbers from the trial reports unless your project is an overview. Many journal editors follow ICMJE rules on overlap and prior publication. Follow those norms and your manuscript stays clean.
Practical Template You Can Copy
Methods Snippet For A Trial-Level Review
“We designed a systematic review of randomized and non-randomized trials. We used prior syntheses to identify search terms and seed records, then ran a librarian-aided strategy in MEDLINE, Embase, CENTRAL, and ClinicalTrials.gov from inception to March 2025. Two reviewers screened records in duplicate, extracted trial-level data, and judged risk of bias with design-specific tools. We didn’t use pooled estimates from prior syntheses.”
Methods Snippet For An Overview Of Reviews
“We designed an overview of reviews on this topic. We searched for systematic reviews in MEDLINE, Embase, Epistemonikos, and trial registries up to March 2025. Two reviewers screened in duplicate. We charted primary study overlap, appraised each review with AMSTAR 2, and summarized review-level effect estimates, re-calculating where models or time points misaligned with our plan.”
Bottom Line For Authors
You can cite prior syntheses for background, scoping, and search leads. For a standard trial-level medical review, extract data from the trials. If your aim is to summarize the syntheses themselves, pick an overview design, plan for overlap, appraise the source reviews, and state the path you took in clear text. That balance keeps methods tight and keeps your conclusions believable.