PEO vs SPIDER is a practical choice when planning a nursing dissertation search: do you need a simple population–exposure–outcome structure, or a more detailed map of the evidence you intend to include? Neither framework automatically produces a complete database strategy.
Use the framework to clarify the question, then decide which concepts should become searchable blocks. Test those decisions against relevant papers and the capabilities of each database. This guide works through that process with a fictional nursing review question rather than treating either acronym as a universal winner.
PEO vs SPIDER: the central difference
PEO stands for Population, Exposure and Outcome. It can provide a compact way to express who or what the review concerns, the exposure or experience being considered, and the outcome of interest. University library guidance presents PEO as one available question framework, rather than a requirement for every review (London South Bank University, n.d.).
SPIDER stands for Sample, Phenomenon of Interest, Design, Evaluation and Research type. Cooke, Smith and Booth (2012) introduced it for qualitative and mixed-method evidence searching. The additional elements encourage you to think explicitly about the kind of study and the experiences or evaluations you want to examine.
The distinction is useful, but it should not become a contest between acronyms. A clear question mapped with PEO can support a thoughtful qualitative search. A detailed SPIDER table can still produce a poor search if every cell becomes a restrictive mandatory term.
For a broad overview of other frameworks, see our nursing research question guide. The focus here is narrower: choosing between PEO and SPIDER, translating that choice into search blocks, and documenting the consequences.
Begin with the evidence your dissertation needs
Before filling a table, identify the kind of answer you need. Are you estimating an intervention’s effects, exploring experiences, mapping a field or examining associations? A question about how people experience care requires different evidence from a question about whether an intervention changes a measured outcome.
Write a one-sentence purpose statement. For example: “This review will explore how older adults describe communication about changes to medicines when leaving hospital.” That statement tells you more about the desired evidence than beginning with a list of database terms.
Next identify the decisions that would determine study eligibility. These might include the population, setting, relevant experience and whether a study actually reports participants’ accounts. Separate genuine eligibility requirements from convenient search filters. A condition can matter at screening even when it is not included as a search term.
Do not select a framework solely because another student used it. Your programme may specify an approach, but if it leaves the choice open, justify the framework in relation to the review’s purpose. Explain what it clarifies and what still needs to be decided.
A worked nursing question mapped both ways
The following review is a fictional planning example. Its scope and search strings are illustrative. They are not a validated or completed search, and no number of retrieved studies is being claimed.
The provisional question is: “How do older adults describe communication about medicine changes during discharge from an acute hospital?” The intended evidence concerns reported experiences, understanding and participation, rather than a numerical estimate of the effectiveness of a particular discharge intervention.
| Framework element | Worked example | Planning consequence |
|---|---|---|
| PEO: Population | Older adults leaving an acute hospital | Define age and setting eligibility. |
| PEO: Exposure | Communication about medicine changes at discharge | Identify discharge and medicines concepts. |
| PEO: Outcome | Experiences, understanding and perceived involvement | Avoid assuming every paper names these in its abstract. |
| SPIDER: Sample | Older adults with the relevant discharge experience | Clarify whose accounts are eligible. |
| SPIDER: Phenomenon of Interest | Communication about changed medicines | Identify the central experience. |
| SPIDER: Design | Eligible interview, focus-group or other specified qualitative designs | Justify design eligibility separately from search syntax. |
| SPIDER: Evaluation | Perceptions, understanding and involvement | Clarify what the analysis will examine. |
| SPIDER: Research type | Qualitative studies and eligible qualitative components of mixed-method studies | State how extractable qualitative evidence will be handled. |
Neither mapping resolves every ambiguity. You still need to decide whether care-home discharge, carers’ accounts, community follow-up and medicine changes without discharge are within scope. The value of the table is making those decisions visible before they become inconsistent screening judgements.
Do not confuse a question framework with a search equation
A framework organises thinking. A database search is an operational expression built using the database’s indexing, fields and syntax. Copying every framework element into an AND-connected block can make the search unnecessarily restrictive.
For example, a relevant interview study may describe “patients’ accounts” rather than “experience”. Another might report interviews in the methods section but omit that term from searchable title and abstract fields. A design block can therefore exclude material even when the design would satisfy your eligibility criteria.
Conversely, removing every population or setting concept can produce a search that is too broad for the review’s purpose and available resources. The answer is to test the proposed strategy, not to assume that either maximum breadth or maximum restriction is always correct.
Keep two adjacent planning columns: “Required for eligibility” and “Included in the search”. Explain differences between them. This small step prevents an examiner from having to guess why an important inclusion criterion does not appear in the final search string.
Build candidate concept blocks
Start with the question’s central concepts. For the fictional example, candidate blocks might cover older adults, hospital discharge and medicines communication. Within each block, identify alternative terms that genuinely describe the same concept.
Combine synonyms with OR and separate essential concepts with AND. Use parentheses so the intended grouping is clear. However, treat the following as a sketch of the logic, not a string that can be pasted unchanged into every database:
(older adult* OR older people OR geriatric*) AND (hospital discharge OR discharge planning) AND (medication* OR medicine*) AND (communicat* OR information OR counsel*)
Some of these terms are broad or context-dependent. “Information” may retrieve unrelated material, while a narrowly phrased discharge term may miss papers using another expression. Inspect relevant records before deciding which alternatives belong in the strategy.
Consider controlled vocabulary alongside free text. The available subject headings and explosion options differ across databases. Identify the actual indexed terms in the database you are using; do not invent a subject heading because it sounds like a plausible academic phrase.
Test PEO vs SPIDER with a search comparison log
Create two candidate strategies that differ in a clearly described way. For example, the first might use the core topic concepts, while the second adds a qualitative design or evaluation block inspired by SPIDER. Run both in the same database on the same date where possible.
Record the complete syntax, fields, limits and retrieval counts. Then examine whether the additional restriction changes the usefulness of the results. A smaller number is not automatically an improvement, and a larger number is not automatically a more complete search.
If you already have a few clearly relevant papers, use them as diagnostic examples. Check whether each strategy retrieves them and investigate any misses. These papers are useful test cases, but they do not prove that the search captures all relevant evidence.
Methley et al. (2014) compared PICO, PICOS and SPIDER in a specific qualitative review context and examined sensitivity and specificity. Their findings support examining trade-offs rather than assuming that the most detailed framework will always retrieve the best evidence.
Do not report sensitivity or precision figures that you have not actually calculated using an appropriate reference set and method. In a dissertation, a transparent account of test searches and known-paper checks may be more defensible than borrowing performance claims from another topic.
Decide when an outcome or evaluation block is helpful
An outcome or evaluation block can be useful when it captures terminology that relevant studies consistently use. It may also help distinguish your question from a much broader literature. Nevertheless, experiential concepts are often expressed in several ways.
For the worked example, “understanding”, “confidence”, “participation” and “experience” are related but not interchangeable. Requiring one of these words could shape which accounts are visible before screening even begins. Ask whether your review genuinely excludes other relevant experiences or whether the block is narrowing the search for convenience.
Test the block against the titles, abstracts and indexing of relevant records. If it repeatedly excludes eligible-looking papers, consider whether eligibility can instead be assessed during screening. Document the decision and any implications for workload.
Do not compensate for a narrow block by adding a long list of weakly related terms without examining them. Every additional term should have a reason. A search strategy should be readable enough for you to explain, even when the final database syntax is necessarily detailed.
Handle qualitative and mixed-method evidence carefully
SPIDER’s research-type element encourages an explicit decision about qualitative and mixed-method studies. State whether a mixed-method paper is eligible only when its qualitative findings can be identified and extracted separately. Explain what you will do when the relevant material is not available in the published report.
A study label alone is not enough. Some papers use “mixed methods” broadly, while others contain qualitative data without prominent qualitative wording in the title. Your screening process should examine the actual methods and findings against the stated criteria.
Also consider whether the design restriction follows from the review question. If you require participants’ experiences, excluding all observational or open-text material merely because it is not labelled an interview may need justification. Equally, expanding eligible designs can change the appraisal and synthesis requirements.
Consult your supervisor before broadening the evidence types late in the process. Changing the framework table after screening to accommodate convenient papers can make the method appear inconsistent unless the amendment and its reasons are reported transparently.
Translate the strategy across databases
A search tested in one interface must be adapted for another. Field codes, phrase handling, truncation, proximity operators and subject headings can differ. Keep the conceptual structure consistent while translating the actual commands.
For each database, record its name and platform. A database can be available through different interfaces with different syntax. Naming only “MEDLINE”, for example, may not explain how a search was executed.
After translation, check whether the database interpreted the search as intended. Review warning messages, search history and a sample of retrieved records. A string accepted without an error message can still behave differently from what you expected.
Keep a version history. If a search is revised after testing, preserve the earlier version and explain the change. This makes it easier to distinguish planned development from an undocumented search selected solely because it produced a convenient number of papers.
Write a defensible framework justification
A useful justification links the framework to the question and separates it from search testing. For example, a student could explain that SPIDER helped specify the intended experiences and eligible evidence types, while the final database strategy used only selected searchable concepts after pilot testing.
Do not copy that wording unless it describes what you actually did. If PEO provided the clearer structure, explain that choice and describe how qualitative terminology or eligibility criteria were handled separately.
University College London’s guidance presents research-question frameworks as aids to planning rather than a mandatory feature of every search (University College London, n.d.). This helps keep the emphasis on a coherent, transparent method instead of choosing an acronym for appearance.
Link the justification to the rest of the review. The question, eligibility criteria, search, extraction plan and synthesis should concern the same evidence need. A well-written framework table cannot resolve contradictions between those stages.
A practical planning and reporting checklist
- State the question and intended evidence type before selecting a framework.
- Map the same question with PEO and SPIDER if the choice is uncertain.
- Define ambiguous population, setting and experience boundaries.
- Separate eligibility requirements from searchable concepts.
- Develop free-text and controlled-vocabulary terms.
- Test additional design or evaluation blocks rather than assuming their value.
- Check known relevant papers and investigate misses.
- Translate syntax for each database and retain the search history.
- Report dates, platforms, complete strategies and amendments.
Ask a librarian or supervisor to review the strategy where support is available. Give them the question, eligibility criteria and test records as well as the string. That context makes feedback more useful than asking only whether the terms “look right”.
Keep a record of decisions that change the review’s scope
Search development can reveal that your initial wording is ambiguous. In the discharge example, a paper might include older adults alongside younger participants, or discuss medicine information as one part of a broader discharge experience. Decide how such cases will be handled before screening large numbers of records.
Record whether subgroup evidence must be separately extractable and what information is needed to establish the relevant experience. If a decision changes eligibility rather than merely improving terminology, identify it as a scope amendment. Check whether earlier screening decisions now need review.
Keep workload considerations transparent. A dissertation has practical limits, but a restriction introduced to make screening manageable should not be presented as though it follows inevitably from PEO or SPIDER. Explain the reason, its timing and the evidence it may exclude.
This record also helps during writing. Instead of reconstructing the method from memory, you can describe the actual sequence of question refinement, pilot searching and protocol decisions. The result is a more coherent account of why the final strategy fits the final question.
Frequently asked questions
Is SPIDER always better for qualitative nursing reviews?
No. It can clarify qualitative evidence needs, but its practical usefulness depends on the question, terminology and how the search is constructed. Test the strategy in your topic area rather than relying on the framework’s label.
Can PEO be used for experiences?
It can help organise a question involving a population, exposure or experience, and relevant outcomes. Define what you mean by outcome and explain how the intended evidence will answer the question.
Must every SPIDER element appear in the database search?
No. Some elements may be better assessed during screening. Explain why each included block is necessary and test whether additional blocks exclude relevant records.
Does “Sample” mean sample size?
No. In SPIDER, it identifies the people or group whose evidence is relevant. Sample size is a separate characteristic to extract or appraise where appropriate.
Can I change frameworks after starting the review?
A change may be justified, but document the reason, timing and consequences. Check whether the question or eligibility criteria also changed and whether searches or screening need to be repeated.
Conclusion and further guidance
Choose PEO or SPIDER for the clarity it brings to your nursing question. Then build, test and document the actual search. The strongest justification explains why each decision helps locate the evidence needed, including why some framework elements are left for screening.
For feedback on your planned method, explore nursing systematic review support and the Nursing Dissertation Service homepage. Read About Us, How It Works and reviews, or request a search-plan review. Use feedback to improve your own work and retain responsibility for the final search and submission.
Featured photograph: Tat Linh Nguyen / Unsplash. Illustrative stock image; it does not depict the studies or participants discussed.
References
Cooke, A., Smith, D. and Booth, A. (2012) ‘Beyond PICO: The SPIDER tool for qualitative evidence synthesis’, Qualitative Health Research, 22(10), pp. 1435–1443. Available at: https://doi.org/10.1177/1049732312452938 (Accessed: 17 October 2026).
London South Bank University (n.d.) PEO: Question frameworks. Available at: https://library.lsbu.ac.uk/questionframeworks/peo (Accessed: 17 October 2026).
Methley, A.M., Campbell, S., Chew-Graham, C., McNally, R. and Cheraghi-Sohi, S. (2014) ‘PICO, PICOS and SPIDER: A comparison study of specificity and sensitivity in three search tools for qualitative systematic reviews’, BMC Health Services Research, 14, 579. Available at: https://doi.org/10.1186/s12913-014-0579-0 (Accessed: 17 October 2026).
University College London (n.d.) Research question frameworks. Available at: https://library-guides.ucl.ac.uk/systematic-searching/research-question-frameworks (Accessed: 17 October 2026).
