Build structured eligibility criteria using the PICOS framework. Define your population, intervention, comparator, outcomes, and study design, then export a formatted criteria table or narrative paragraph for your protocol.
Add any additional reasons for excluding studies that are not covered by the PICOS framework above.
Specify your target population including age range, sex, clinical setting, and diagnostic criteria. Be precise enough that two reviewers would agree on eligibility.
Describe the primary intervention under study, including dosage and delivery method. Define what the intervention is being compared against (placebo, standard care, etc.).
Add your primary and secondary outcomes with measurement tools or scales. Specify the minimum follow-up period required for study inclusion.
Select which study designs to include, set publication date ranges and language restrictions, and add any additional exclusion criteria specific to your review.
The PICOS framework ensures you address all five key dimensions of study eligibility. Structured criteria reduce ambiguity during screening, improve inter-rater agreement, and make your review methods transparent and reproducible.
Define and register your eligibility criteria before running database searches. Post-hoc changes to criteria after seeing results introduce selection bias. Register your protocol on PROSPERO or publish it in a journal to lock in your criteria.
PROSPERO requires explicit eligibility criteria for each PICOS element. Using this tool ensures you have structured, complete criteria ready to paste into the PROSPERO registration form, reducing the risk of incomplete reporting.
If you must modify criteria after beginning screening, document the change, the rationale, and the date. Report all amendments in your review manuscript. Unexplained changes to eligibility criteria are a red flag for reviewers and editors.
A PICOS criteria generator operationalises the structured framework that the Cochrane Handbook (Higgins et al., 2023, Chapter 3) identifies as the cornerstone of every systematic review protocol. PICOS decomposes the review question into five elements—Population, Intervention, Comparator, Outcome, and Study design—so that two independent screeners can apply the same decision rules with minimal ambiguity. Richardson et al. (1995) originally proposed the PICO framework for clinical question formulation; the subsequent addition of the Study-design element reflects the reality that restricting a review to randomised controlled trials, for instance, demands an explicit a priori declaration. Before defining detailed criteria, researchers should first articulate a focused research question using our PICO framework builder, which structures the question into its constituent elements and ensures that every PICOS dimension is addressed before screening begins. For qualitative or mixed-methods evidence syntheses, the SPIDER framework (Cooke et al., 2012) replaces Intervention and Comparator with Phenomenon of Interest, Design, Evaluation, and Research type, offering a more natural fit when the question concerns lived experiences rather than treatment effects. For diagnostic accuracy reviews, the QUADAS-2 framework (Whiting et al., 2011) provides a complementary set of eligibility considerations covering patient selection, index test, reference standard, and flow and timing.
An inclusion exclusion criteria tool must enforce the pre-specification principle that PRISMA 2020 (Page et al., 2021) codifies in its checklist: eligibility criteria should be defined and registered before the literature search is executed, not modified retrospectively in response to search results. Post-hoc changes introduce selection bias and undermine the transparency that distinguishes a systematic review from a narrative one. The JBI Manual (Aromataris & Munn, 2020) recommends pilot-testing criteria on a random sample of 50 abstracts, measuring inter-rater agreement, and refining any ambiguous wording before full screening commences. A Cohen's kappa of at least 0.60 during pilot screening is generally considered the minimum acceptable inter-rater agreement threshold before proceeding to full screening. Screening software such as Covidence and EPPI-Reviewer operationalises these criteria by allowing reviewers to apply structured eligibility rules at scale, with built-in conflict resolution and agreement reporting. Once criteria are finalised, translating them into Boolean search strings is the next step; our search strategy builder converts PICOS elements into database-specific queries for PubMed, Embase, and the Cochrane Central Register, keeping the search deliberately broader than the eligibility criteria so that borderline studies are captured during screening rather than missed during retrieval.
Systematic review eligibility criteria feed directly into protocol registration, PRISMA flow documentation, and data extraction planning. The Cochrane Handbook (Higgins et al., 2023, Chapter 3) states that every protocol submitted to PROSPERO must enumerate inclusion and exclusion rules for each PICOS element in sufficient detail that the review could be replicated by an independent team. Our PROSPERO registration formatter accepts the structured output from this criteria builder and maps it to the required registration fields, reducing transcription errors and ensuring completeness. The criteria also determine the denominators in the PRISMA flow diagram—how many records were excluded at title/abstract screening versus full-text review—which our PRISMA flow generator renders as a publication-ready figure with exclusion reasons linked back to specific PICOS elements. For living systematic reviews, eligibility criteria must also include temporal updating rules that define how frequently new evidence is incorporated and what triggers a re-screening cycle.
Methodological rigour requires that eligibility decisions are documented at the study level, not merely summarised in aggregate. PRISMA 2020 (Page et al., 2021) now mandates a list of studies excluded at the full-text stage together with the reason for each exclusion, a requirement that underscores the need for unambiguous, pre-specified criteria. The JBI Manual (Aromataris & Munn, 2020) extends this guidance to scoping and qualitative reviews, adapting the PICOS framework into PCC (Population, Concept, Context) for non-interventional questions. Regardless of the framework chosen, the eligibility criteria ultimately shape the data that will be extracted; our data extraction template builder aligns its fields with the PICOS elements defined here, creating a seamless workflow from question formulation through screening to quantitative synthesis. By enforcing structure, transparency, and pre-registration, this tool helps review teams meet the methodological standards that Cochrane, JBI, and PRISMA 2020 set for trustworthy evidence synthesis.
PICOS stands for Population, Intervention, Comparator, Outcome, and Study design. It is a structured framework used to define eligibility criteria for systematic reviews. Each element specifies which studies should be included or excluded. PICOS extends the PICO framework by explicitly adding study design as a fifth element, which is particularly useful when you want to restrict your review to certain methodologies such as RCTs only.
Start by formulating your research question using PICOS. For each element, specify the characteristics that make a study eligible (inclusion criteria) and those that make it ineligible (exclusion criteria). Be as specific as possible: define clinical conditions using diagnostic criteria, specify age ranges, list acceptable study designs, and name the outcome measures you will extract. Pre-register your criteria in PROSPERO or a protocol paper before beginning your search.
Common mistakes include: (1) being too broad, which increases screening workload without improving the review; (2) being too narrow, which may miss relevant studies; (3) using vague language such as 'relevant outcomes' instead of naming specific measures; (4) adding post-hoc criteria after seeing search results, which introduces bias; and (5) failing to pilot-test criteria on a sample of abstracts before full screening.
Use PICOS for quantitative systematic reviews, especially those involving intervention studies (RCTs, quasi-experimental designs). SPIDER (Sample, Phenomenon of Interest, Design, Evaluation, Research type) is better suited for qualitative or mixed-methods reviews where the concepts of 'intervention' and 'comparator' do not apply. If your review focuses on experiences, perceptions, or qualitative phenomena, SPIDER provides a more natural framework.
Eligibility criteria directly inform your search strategy. The Population and Intervention elements translate into search terms and Boolean queries for databases like PubMed and Embase. Study design filters (e.g., Cochrane Highly Sensitive Search Strategy for RCTs) can narrow results. However, keep your search broader than your inclusion criteria to avoid missing relevant studies. Apply strict criteria during screening, not during searching.
Yes. The Cochrane Handbook recommends pilot testing eligibility criteria on a random sample of 20–50 titles/abstracts before full screening. Two reviewers independently apply the criteria, then calculate inter-rater agreement (e.g., Cohen’s κ ≥ 0.60). Discrepancies reveal ambiguous criteria that need clarification. Refine and re-pilot until agreement is acceptable. Document any changes to criteria during this process.
Inclusion criteria define the characteristics a study must have to be eligible (e.g., RCT design, adult population, published in English). Exclusion criteria specify characteristics that disqualify otherwise eligible studies (e.g., sample size < 10, conference abstracts only, animal studies). Together they form the eligibility framework. PRISMA 2020 requires reporting both in the methods section with clear rationale.
Decide at the protocol stage whether to restrict by language. Language restrictions can introduce bias (Cochrane discourages them), but practical constraints exist. Options include: including all languages and using translation services or Google Translate for screening, restricting to languages your team can read (report this limitation), or excluding only at full-text stage with the count reported in the PRISMA flow diagram.
Our methodologists can help you define eligibility criteria, develop search strategies, register on PROSPERO, and build data extraction forms for your entire systematic review.