How long should the methods section of a systematic review be?

The methods section typically ranges from 1,500 to 3,000 words depending on review complexity. Reviews with multiple outcomes and subgroup analyses tend to be longer. Some journals require detailed methods in supplementary appendices due to word limits.

What is the difference between PRISMA 2020 Items 11 and 15?

Item 11 addresses risk of bias within individual studies using tools like RoB 2 or ROBINS-I. Item 15 addresses risk of bias across the entire synthesis, specifically whether missing results from publication bias or selective reporting have distorted the pooled estimate.

Should I include the full search strategy in the main manuscript or in a supplement?

Most journals expect the full search strategy in a supplementary appendix with a summary in the main text. PRISMA 2020 requires the full strategy for at least one database to be reproducible and accessible.

Can I use a single reviewer for screening and data extraction?

Single-reviewer screening is a significant limitation. The Cochrane Handbook recommends independent dual screening and dual data extraction. If resources are limited, have a second reviewer verify at least 20 percent of screened records and all extracted data.

How do I report protocol deviations without weakening my manuscript?

Report each deviation transparently with the original plan, the change, the rationale, and timing. Pre-data deviations are less concerning than post-data changes. Label post-data analyses as exploratory.

What certainty assessment framework should I use?

GRADE is the most widely accepted framework and is required by the Cochrane Collaboration. It rates certainty as high, moderate, low, or very low based on risk of bias, inconsistency, indirectness, imprecision, and publication bias.

Methods Section Systematic Review: Guide

The methods section of a systematic review describes exactly how you identified, selected, appraised, and synthesized the evidence. Under PRISMA 2020 (Page et al., 2021), the methods section spans Items 5 through 16, covering everything from eligibility criteria to certainty assessment. A well-written methods section allows any reader to replicate your review, and it is the section that peer reviewers scrutinize most closely. If a reviewer cannot follow your methods, they will reject the manuscript regardless of your findings. This guide covers each PRISMA 2020 methods sub-item in order, provides example sentences you can adapt, flags the most common reviewer criticisms for each section, and explains how to report protocol deviations and cite the tools you used.

Before writing your methods section, you should have a registered protocol, a completed search, and finalized data extraction. If you have not yet reached that stage, start with our step-by-step guide to writing a systematic review for the full workflow from question formulation to manuscript submission.

Eligibility Criteria: PRISMA 2020 Item 5

PRISMA 2020 Item 5 requires you to specify the inclusion and exclusion criteria for your review, including the study characteristics (population, intervention, comparator, outcome, and study design) and the report characteristics (language, publication status, and date range). The Cochrane Handbook (Higgins et al., 2023) recommends structuring eligibility criteria around the PICO framework (or PECO for observational reviews), which ensures every element of your research question maps directly to a criterion.

What this subsection must contain:

The population, intervention or exposure, comparator, and outcome definitions, stated with enough specificity that a second reviewer could independently apply them
The study designs eligible for inclusion (randomized controlled trials only, or observational studies as well)
Any restrictions on language, publication date, or publication status (conference abstracts, preprints, grey literature)
Justification for each restriction, because reviewers will question any limitation that could introduce selection bias

Example paragraph:

We included randomized controlled trials and quasi-experimental studies that enrolled adults aged 18 years or older diagnosed with type 2 diabetes mellitus (Population), compared a structured exercise intervention of at least 12 weeks (Intervention) with usual care or no intervention (Comparator), and reported glycated hemoglobin as a primary outcome (Outcome). We excluded case reports, case series, narrative reviews, and conference abstracts without full-text availability. No language or date restrictions were applied.

Common reviewer criticisms:

"The eligibility criteria are vague. How do you define 'structured exercise'?" Reviewers want operational definitions, not general terms.
"Why did you exclude non-English studies? This could bias your results." Always justify language restrictions with a citation or practical rationale.
"You did not specify the minimum follow-up period." If your outcome requires a time horizon, state it explicitly.

Use our free inclusion and exclusion criteria builder to structure your PICO or PECO elements into a formatted criteria table before drafting this section.

Information Sources: PRISMA 2020 Item 6

PRISMA 2020 Item 6 requires you to list all databases, registers, websites, organizations, reference lists, and other sources you searched or consulted to identify studies. You must also report the date of the most recent search for each source. The Cochrane Handbook recommends searching at least MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials (CENTRAL) for intervention reviews, plus discipline-specific databases relevant to your topic.

What this subsection must contain:

The full name of every database searched (not just abbreviations)
The platform or interface used for each database (for example, "MEDLINE via PubMed" or "MEDLINE via Ovid")
The date of the last search for each database
Any additional sources: trial registries (ClinicalTrials.gov, WHO ICTRP), grey literature databases (OpenGrey, ProQuest Dissertations), reference lists of included studies, forward citation tracking, and contact with study authors

Example paragraph:

We searched MEDLINE (via PubMed), Embase (via Ovid), the Cochrane Central Register of Controlled Trials (CENTRAL), CINAHL (via EBSCOhost), and PsycINFO (via Ovid) from inception to March 15, 2026. We also searched ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform for ongoing or unpublished studies. Reference lists of all included studies and relevant systematic reviews were screened for additional eligible records. No grey literature databases were searched.

Common reviewer criticisms:

"You searched only one database. This is insufficient for a systematic review." Two databases is the bare minimum; three or more is standard.
"You did not report the search dates." Without dates, the review is not reproducible.
"Why did you not search Embase? You may have missed European and pharmacological literature." Justify any omission of major databases.

Search Strategy: PRISMA 2020 Item 7

PRISMA 2020 Item 7 requires you to present the full search strategy for at least one database, including any filters or limits used. The complete search strategies for all databases should be available in a supplementary file. This is where many methods sections fail, because authors provide only a list of keywords rather than a reproducible search string with Boolean operators, MeSH terms, and field tags.

What this subsection must contain:

A statement that the full search strategy is available in a supplementary appendix
The key concepts combined with Boolean operators (AND, OR)
Whether controlled vocabulary (MeSH, Emtree) was used alongside free-text terms
Any filters applied (study design filters, date limits, language filters)
Whether a librarian or information specialist developed or peer-reviewed the search strategy, and if so, using which framework (such as the PRESS checklist)

Example paragraph:

The search strategy was developed in consultation with a health sciences librarian and peer-reviewed using the PRESS (Peer Review of Electronic Search Strategies) checklist. The strategy combined terms for the population (type 2 diabetes mellitus), the intervention (exercise, physical activity, resistance training), and the outcome (glycated hemoglobin, HbA1c) using Boolean operators. Both MeSH terms and free-text synonyms were used. No study design filters were applied. The complete search strategy for all five databases is provided in Supplementary Appendix A.

Common reviewer criticisms:

"The search strategy is not reproducible. You listed keywords but did not show the actual search string." Always include the full string with Boolean logic and field tags.
"You did not use controlled vocabulary. Free-text only searches miss indexed records." Combine MeSH/Emtree with free-text for comprehensive retrieval.
"There is no evidence the search was peer-reviewed." Librarian involvement and PRESS review strengthen credibility.

Build your search strings systematically using the free search strategy builder, and refer to our search strategy guide for detailed instructions on combining controlled vocabulary with free-text terms across multiple databases.

Selection Process: PRISMA 2020 Item 8

PRISMA 2020 Item 8 requires you to describe the process used to select studies for inclusion, including the number of reviewers at each stage, how disagreements were resolved, and any automation tools or software used. The Cochrane Handbook mandates independent dual screening at both the title-abstract and full-text stages.

What this subsection must contain:

How many reviewers independently screened titles and abstracts, and how many screened full texts
The software or tool used for screening (Covidence, Rayyan, Abstrackr, or manual spreadsheet)
How disagreements between reviewers were resolved (discussion, third reviewer, consensus)
Whether a calibration or pilot screening exercise was conducted before formal screening began
The inter-rater reliability statistic, if calculated (Cohen's kappa or percentage agreement)

Example paragraph:

Two reviewers (S.M. and J.K.) independently screened all titles and abstracts using Covidence systematic review software. Records marked as "include" or "maybe" by either reviewer advanced to full-text screening. Both reviewers then independently assessed full-text articles against the predefined eligibility criteria. Disagreements were resolved through discussion; a third reviewer (A.L.) arbitrated when consensus could not be reached. Before formal screening, both reviewers independently screened a pilot batch of 50 records to calibrate inclusion criteria. Inter-rater agreement at the title-abstract stage was substantial (Cohen's kappa = 0.82).

Common reviewer criticisms:

"Only one reviewer screened the records. This introduces selection bias." Single-reviewer screening is a critical methodological weakness.
"You did not describe how disagreements were resolved." Always state the resolution mechanism.
"What software did you use? This affects reproducibility." Name the tool and version.

Data Collection Process: PRISMA 2020 Item 9

PRISMA 2020 Item 9 covers how data were extracted from included studies, including the number of reviewers who independently extracted data, how disagreements were handled, any automation tools used, and how missing data were obtained from study authors.

What this subsection must contain:

The number of reviewers who independently extracted data
Whether a standardized data extraction form was used, and if it was piloted
The specific data items extracted (see Item 10 for the list)
How discrepancies between extractors were resolved
Whether and how study authors were contacted for missing or unclear data

Example paragraph:

Data were extracted independently by two reviewers using a standardized form piloted on three included studies. Extracted items included study characteristics (author, year, country, study design), participant characteristics (sample size, age, sex, baseline glycated hemoglobin), intervention details (type, frequency, duration, supervision), comparator details, and outcome data (mean, standard deviation, and sample size at each time point). Discrepancies between extractors were resolved by discussion, with a third reviewer consulted when agreement could not be reached. Authors of five studies were contacted by email to obtain missing standard deviations; three responded within four weeks.

Common reviewer criticisms:

"Data were extracted by only one reviewer. This is a significant limitation." Dual extraction is the standard for minimizing transcription errors.
"You did not describe the data extraction form or pilot it." Piloting catches ambiguities in the form before full extraction begins.
"How did you handle studies that reported medians and interquartile ranges instead of means and standard deviations?" Describe any conversion methods used (such as Wan et al., 2014 or Luo et al., 2018 estimators).

Study Risk of Bias Assessment: PRISMA 2020 Item 11

PRISMA 2020 Item 11 requires you to describe the methods used to assess the risk of bias in each included study, including the tool used, the domains assessed, and the number of reviewers who independently applied the tool. The Cochrane Handbook (Higgins et al., 2023) recommends RoB 2 for randomized trials and ROBINS-I for non-randomized studies.

What this subsection must contain:

The specific risk of bias tool used, with a citation
The domains assessed by that tool (for example, RoB 2 assesses randomization, deviations from intended interventions, missing outcome data, measurement of outcome, and selection of reported result)
The number of reviewers who independently assessed each study
How disagreements in risk of bias judgments were resolved
Whether risk of bias assessments were used in sensitivity analyses or to judge the certainty of evidence

Example paragraph:

Risk of bias in randomized controlled trials was assessed using the Cochrane Risk of Bias 2 (RoB 2) tool (Sterne et al., 2019). Each study was evaluated across five domains: bias arising from the randomization process, bias due to deviations from intended interventions, bias due to missing outcome data, bias in measurement of the outcome, and bias in selection of the reported result. Two reviewers independently assessed each study, and disagreements were resolved by discussion with a third reviewer. Overall risk of bias for each study was classified as low, some concerns, or high. Studies rated as high risk of bias were included in the primary analysis but examined separately in a sensitivity analysis.

Common reviewer criticisms:

"You used the Newcastle-Ottawa Scale for randomized trials. NOS is designed for observational studies." Match the tool to the study design.
"Risk of bias was assessed by only one reviewer." Independent dual assessment is required.
"You did not describe how risk of bias judgments informed your synthesis." Explain whether high-risk studies were excluded from sensitivity analyses or downgraded in certainty assessment.

Effect Measures: PRISMA 2020 Item 12

PRISMA 2020 Item 12 requires you to specify the effect measures used for each outcome (for example, risk ratio, odds ratio, mean difference, standardized mean difference, hazard ratio) and how they were selected.

What this subsection must contain:

The primary effect measure for each outcome type (dichotomous, continuous, time-to-event)
The rationale for choosing that measure
Whether 95 percent confidence intervals were reported
Any transformations applied (such as converting odds ratios to risk ratios, or using Hedges' g instead of Cohen's d for small samples)

Example paragraph:

For continuous outcomes, we calculated the mean difference when studies used the same measurement scale and the standardized mean difference (Hedges' g) when different scales were used. For dichotomous outcomes, we calculated risk ratios with 95 percent confidence intervals. Risk ratios were preferred over odds ratios because they are more interpretable when event rates are not rare. For time-to-event outcomes, we extracted or calculated hazard ratios with 95 percent confidence intervals.

Common reviewer criticisms:

"Why did you use odds ratios when event rates exceed 20 percent? Odds ratios overestimate the effect in common outcomes." Justify the choice of effect measure relative to event frequency.
"You did not specify whether you used Cohen's d or Hedges' g." Small-sample corrections matter; name the exact estimator.
"Confidence intervals are missing for some outcomes." Always report both point estimates and intervals.

Struggling to draft a methods section that will satisfy peer reviewers? Research Gold's methodologists write and review methods sections for systematic reviews and meta-analyses across all clinical and social science disciplines. If you need expert feedback on your eligibility criteria, search strategy, or synthesis approach, request a free quote and tell us which sections you need help with. We also provide full systematic review services from protocol to publication.

Synthesis Methods: PRISMA 2020 Item 13

PRISMA 2020 Item 13 is the most detailed methods item. It requires you to describe every step of your data synthesis, whether narrative or quantitative. If you conducted a meta-analysis, this section must cover the statistical model, the method for estimating heterogeneity, the software used, and any additional analyses (subgroup, sensitivity, meta-regression).

What this subsection must contain for a meta-analysis:

Whether a fixed-effect or random-effects model was used, and why
The heterogeneity estimator (DerSimonian-Laird, restricted maximum likelihood, Paule-Mandel, or another method)
The heterogeneity statistics reported (Cochran's Q, I-squared, tau-squared, prediction interval)
The statistical software and version (such as R version 4.3.2 with the metafor package, or Review Manager 5.4, or Stata 18)
Subgroup analyses planned a priori, including the variables tested and the minimum number of studies required per subgroup
Sensitivity analyses conducted (leave-one-out, exclusion of high risk of bias studies, fixed-effect vs. random-effects comparison)
Whether publication bias was assessed (see Item 15)

What this subsection must contain for a narrative synthesis:

The framework used for narrative synthesis (such as Synthesis Without Meta-analysis, or SWiM, reporting guidelines)
How studies were grouped for narrative comparison
How effect direction and magnitude were described across studies
Whether vote counting or harvest plots were used

Example paragraph (meta-analysis):

We conducted random-effects meta-analyses using the restricted maximum likelihood (REML) estimator to pool effect sizes. Statistical heterogeneity was assessed using the Cochran Q test (significance threshold p < 0.10) and the I-squared statistic. I-squared values of 25, 50, and 75 percent were interpreted as low, moderate, and high heterogeneity, respectively. Prediction intervals were calculated to estimate the range of true effects across settings. Subgroup analyses were planned a priori for intervention type (aerobic vs. resistance vs. combined exercise), intervention duration (less than 24 weeks vs. 24 weeks or more), and supervision status (supervised vs. unsupervised). Meta-regression was performed when 10 or more studies were available per covariate. Leave-one-out sensitivity analyses were conducted to assess the influence of individual studies. All analyses were performed in R version 4.3.2 using the metafor package (Viechtbauer, 2010).

Common reviewer criticisms:

"You used DerSimonian-Laird but have fewer than 20 studies. REML or Paule-Mandel is more appropriate for small numbers of studies." The choice of heterogeneity estimator matters when the number of studies is small.
"You reported I-squared but not the prediction interval. I-squared describes the proportion of variability, not the range of expected effects." Prediction intervals provide clinical context that I-squared alone cannot.
"Your subgroup analyses were not pre-specified in the protocol." Post hoc subgroup analyses should be clearly labeled as exploratory.
"You did not name the statistical software." Always report the software, version, and specific packages used.

Reporting Bias Assessment: PRISMA 2020 Item 15

PRISMA 2020 Item 15 requires you to describe the methods used to assess the risk of bias due to missing results in the synthesis (commonly called publication bias or reporting bias). This is distinct from the risk of bias within individual studies (Item 11).

What this subsection must contain:

The methods used to assess publication bias (funnel plots, Egger's regression test, Begg's rank correlation test, or trim-and-fill analysis)
The minimum number of studies required before these tests were applied (typically 10 studies for funnel plot-based methods)
Whether selective reporting within studies was assessed (comparing published results with protocols or trial registrations)

Example paragraph:

For meta-analyses that included 10 or more studies, we assessed publication bias visually using funnel plots and statistically using Egger's regression test (Egger et al., 1997). Asymmetry was considered present when Egger's test yielded p < 0.10. For meta-analyses with fewer than 10 studies, we noted that statistical tests for publication bias have low power and results should be interpreted with caution. Selective outcome reporting was assessed by comparing published results with registered protocols on ClinicalTrials.gov or PROSPERO where available.

Common reviewer criticisms:

"You have only 6 studies in this meta-analysis. Funnel plots and Egger's test are unreliable with fewer than 10 studies." Acknowledge this limitation explicitly.
"You did not assess selective reporting bias." Comparing published outcomes with protocol registrations is now expected under PRISMA 2020.
"Your funnel plot shows asymmetry but you did not discuss it." Funnel plot asymmetry requires interpretation: it may indicate publication bias, small-study effects, or genuine heterogeneity.

Certainty Assessment: PRISMA 2020 Item 16

PRISMA 2020 Item 16 requires you to describe the methods used to assess the certainty (or quality) of the body of evidence for each outcome. The most widely used framework is GRADE (Grading of Recommendations, Assessment, Development and Evaluations), which rates certainty as high, moderate, low, or very low based on five domains.

What this subsection must contain:

The framework used (GRADE, or an alternative if justified)
The five GRADE domains assessed: risk of bias, inconsistency, indirectness, imprecision, and publication bias
How certainty ratings were determined and by whom
Whether summary of findings tables were produced (these are strongly recommended by Cochrane)

Example paragraph:

We assessed the certainty of evidence for each primary outcome using the GRADE framework (Guyatt et al., 2011). The certainty of evidence was rated as high, moderate, low, or very low based on five domains: risk of bias across studies, inconsistency of results, indirectness of evidence, imprecision of effect estimates, and publication bias. Two reviewers independently rated each domain, and disagreements were resolved by discussion. Evidence from randomized controlled trials started at high certainty and was downgraded by one or two levels for serious or very serious concerns in each domain. Results were presented in summary of findings tables generated using GRADEpro GDT software.

Common reviewer criticisms:

"You did not use GRADE or any certainty assessment framework." Omitting certainty assessment is a major gap under PRISMA 2020.
"Your GRADE ratings are inconsistent. You rated certainty as high despite serious risk of bias concerns." Each downgrading decision must be justified transparently.
"You did not produce summary of findings tables." Cochrane and most high-impact journals now expect these tables.

How to Report Protocol Deviations

Nearly every systematic review deviates from its registered protocol in some way. PRISMA 2020 requires you to report all deviations transparently, explain why they occurred, and indicate whether they were made before or after data collection. The Cochrane Handbook (Higgins et al., 2023) emphasizes that unreported protocol deviations undermine the credibility of the entire review.

Common types of protocol deviations:

Adding or removing outcomes after seeing the data
Changing the eligibility criteria (for example, broadening the population definition because too few studies met the original criteria)
Using a different risk of bias tool than originally planned
Adding post hoc subgroup analyses that were not specified in the protocol
Changing the statistical model (for example, switching from fixed-effect to random-effects after observing high heterogeneity)

How to report them:

Create a dedicated subsection titled "Deviations from the Registered Protocol" or include a table listing each deviation, the original plan, the change made, and the rationale. Reference your PROSPERO registration number so reviewers can verify the original protocol.

Example paragraph:

This review was registered on PROSPERO (registration number CRD42025XXXXXX). The protocol is available at [link]. Two deviations from the registered protocol occurred. First, we originally planned to include only randomized controlled trials but broadened eligibility to include quasi-experimental studies because the initial search identified only four randomized controlled trials. This change was made before data extraction began. Second, we added a subgroup analysis by participant age group, which was not pre-specified. This analysis is reported as exploratory.

Register your protocol before starting your review using our free PROSPERO registration formatter, and consult our PROSPERO registration guide for step-by-step instructions.

How to Cite Tools and Software in Your Methods Section

Peer reviewers and journal editors expect you to cite every tool, software package, and guideline referenced in your methods section. Proper citation serves two purposes: it allows readers to replicate your methods, and it gives credit to tool developers whose work made your review possible.

Essential citations for a typical systematic review methods section:

Tool or Guideline	What to Cite
PRISMA 2020	Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372:n71.
Cochrane Handbook	Higgins JPT, Thomas J, Chandler J, et al., editors. Cochrane Handbook for Systematic Reviews of Interventions version 6.4. Cochrane; 2023.
RoB 2	Sterne JAC, Savovic J, Page MJ, et al. RoB 2: a revised tool for assessing risk of bias in randomised trials. BMJ. 2019;366:l4898.
ROBINS-I	Sterne JAC, Hernan MA, Reeves BC, et al. ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions. BMJ. 2016;355:i4919.
GRADE	Guyatt GH, Oxman AD, Vist GE, et al. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. BMJ. 2008;336:924-926.
Covidence	Covidence systematic review software, Veritas Health Innovation, Melbourne, Australia. Available at www.covidence.org.
R metafor package	Viechtbauer W. Conducting meta-analyses in R with the metafor package. Journal of Statistical Software. 2010;36(3):1-48.
Review Manager	Review Manager (RevMan) [Computer program]. Version 5.4. The Cochrane Collaboration; 2020.

Where to place citations: Cite each tool the first time you mention it in the methods section. Do not leave tool names uncited. If you used our free PRISMA flow diagram generator or search strategy builder, you can cite Research Gold alongside the relevant guideline.

PRISMA 2020 Methods Checklist: Items 5 through 16 at a Glance

Use this table as a final checklist before submitting your manuscript. Each row corresponds to a PRISMA 2020 methods item.

PRISMA Item	Section	Key Question
Item 5	Eligibility criteria	Did you specify PICO/PECO criteria and justify all restrictions?
Item 6	Information sources	Did you list all databases, platforms, dates, and supplementary sources?
Item 7	Search strategy	Did you provide the full search string and note librarian involvement?
Item 8	Selection process	Did you describe dual screening, software, and disagreement resolution?
Item 9	Data collection	Did you describe dual extraction, piloting, and author contact?
Item 10	Data items	Did you list all extracted variables and any assumptions made?
Item 11	Risk of bias	Did you name the tool, describe domains, and report dual assessment?
Item 12	Effect measures	Did you specify the effect measure for each outcome type and justify?
Item 13	Synthesis methods	Did you describe the model, heterogeneity estimator, software, and planned analyses?
Item 14	Reporting bias methods	Did you describe planned publication bias tests and thresholds?
Item 15	Certainty assessment	Did you describe the GRADE framework and summary of findings tables?
Item 16	Additional analyses	Did you pre-specify subgroup and sensitivity analyses in the protocol?

For a broader understanding of all 27 PRISMA 2020 items beyond the methods section, see our complete PRISMA 2020 guidelines explained.

How to Write the Methods Section of a Systematic Review: PRISMA Checklist Guide

Key Takeaways

Eligibility Criteria: PRISMA 2020 Item 5

Information Sources: PRISMA 2020 Item 6

Search Strategy: PRISMA 2020 Item 7

Selection Process: PRISMA 2020 Item 8

Data Collection Process: PRISMA 2020 Item 9

Frequently Asked Questions

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Study Risk of Bias Assessment: PRISMA 2020 Item 11

Effect Measures: PRISMA 2020 Item 12

Synthesis Methods: PRISMA 2020 Item 13

Reporting Bias Assessment: PRISMA 2020 Item 15

Certainty Assessment: PRISMA 2020 Item 16

How to Report Protocol Deviations

How to Cite Tools and Software in Your Methods Section

PRISMA 2020 Methods Checklist: Items 5 through 16 at a Glance

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