How to Develop Inclusion and Exclusion Criteria
Inclusion and exclusion criteria define which studies belong in your review. They should follow directly from your question, be set before screening, be precise enough for two reviewers to agree, and be justified.
Build them with PICOS
| Element | Questions | Example |
|---|---|---|
| Population | Who? Age, condition, setting | Adults 18+ with type 2 diabetes |
| Intervention/exposure | What? Dose, delivery | Structured exercise at least 8 weeks |
| Comparator | Compared with? | Usual care or no exercise |
| Outcomes | What measured, and when? | HbA1c at 3+ months |
| Study design | Which designs? | Randomised trials |
Add other criteria that are justified: publication period, language, publication status (including or excluding conference abstracts), and minimum sample or follow-up.
Pilot and refine
- Draft criteria.
- Have two reviewers test them on 30–50 records.
- Compare decisions, discuss disagreement and clarify wording.
- Finalise before main screening, and record any later change.
Justify restrictions
Restricting by language or date can introduce bias; explain why you applied them and discuss them as limitations. Excluding studies because they do not report your outcome can hide selective reporting, so consider this carefully.
Illustrative example
Invented for teaching. "Include: randomised trials in adults with chronic low back pain comparing supervised exercise with no exercise or usual care, reporting pain at 6 weeks or longer. Exclude: acute back pain, post-surgical populations, and studies without a control group."
Examples of criteria that need care
Be explicit about definitions that readers might interpret differently, such as "older adults" (age threshold), "randomised" (does quasi-randomised count?), "primary care" and "follow-up" (minimum length). If you restrict to English, say so and discuss the possible effect. If conference abstracts are excluded because they lack detail, state this too. Test each criterion on borderline examples during the pilot.
Common pitfalls
- Vague criteria ("good quality studies").
- Changing criteria after seeing which studies exist.
Key takeaways
- Criteria follow from the question and are set in advance.
- Pilot them and justify restrictions.
References and further reading
- Higgins JPT, Thomas J, Chandler J, et al., editors. Cochrane Handbook for Systematic Reviews of Interventions. Cochrane. Link
- Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372:n71. doi:10.1136/bmj.n71
- Chan AW, Tetzlaff JM, Altman DG, et al. SPIRIT 2013 statement: defining standard protocol items for clinical trials. Ann Intern Med. 2013;158(3):200-207. doi:10.7326/0003-4819-158-3-201301080-00007
Related reading
This page is general educational information about research methods. It is not medical, legal or regulatory advice; follow your institution's ethics board and your target journal's instructions.