Conducting a Mixed Methods Systematic Review: Searching for Quantitative and Qualitative Studies

A mixed methods systematic review synthesizes evidence from both quantitative (e.g., experimental, observational studies like RCTs or cohort studies) and qualitative (e.g., interviews, ethnographies) research to provide a comprehensive understanding of a topic. The search process follows similar principles to a standard systematic review but requires strategies to capture diverse study designs. I'll guide you step by step, focusing on your query about searching for both types of studies. This draws from established frameworks like PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and guidance from the Cochrane Collaboration and Joanna Briggs Institute (JBI) for mixed methods reviews.

1. Define Your Research Question and Inclusion Criteria

• Start with a clear, inclusive question using a framework like PICO (Population, Intervention, Comparison, Outcome) for quantitative aspects, combined with SPICE (Setting, Perspective, Intervention, Comparison, Evaluation) for qualitative ones. For mixed methods, adapt to PICoS or similar to encompass both.


• Example: If reviewing interventions for mental health in workplaces, specify: "What are the quantitative effects and qualitative experiences of mindfulness programs (I) on employee stress (O) in corporate settings (S)?"


• Develop eligibility criteria:


• Quantitative: RCTs, quasi-experimental, surveys with numerical data.


• Qualitative: Thematic analyses, grounded theory, narrative studies.


• Mixed: Studies combining both (e.g., convergent designs).


• Exclude: Opinion pieces, editorials; include gray literature if relevant.


• Tip: Use tools like Covidence or Rayyan for screening later.

2. Develop a Comprehensive Search Strategy

• Key Principle: Design a sensitive search (broad to avoid missing studies) that doesn't overly restrict by method type upfront. Instead, filter post-search. Search for both paradigms simultaneously to ensure overlap and efficiency.


• Identify Databases: Cover biomedical, social sciences, and multidisciplinary sources to capture both types.


• Quantitative-focused: MEDLINE (PubMed), Embase, CINAHL (for nursing/health), Cochrane Library, Web of Science.


• Qualitative-focused: PsycINFO, ERIC (education), Sociological Abstracts, Anthropology Plus.


• Multidisciplinary: Scopus, Google Scholar (for gray literature), ProQuest Dissertations.


• Specialized for mixed methods: JBI Database of Systematic Reviews, Campbell Collaboration.


• Search Terms and Boolean Logic:


• Break into concepts: Population + Intervention/Exposure + Outcome + Study Design (optional).


• Use MeSH/Emtree terms for controlled vocabulary (e.g., in PubMed: "Mindfulness"[Mesh] AND "Workplace"[Mesh]).


• Combine quantitative and qualitative filters sparingly—run broad searches first.


• Broad example: ("mindfulness" OR "meditation") AND ("workplace" OR "employee") AND ("stress" OR "burnout").


• Quantitative-specific terms (add if needed): "randomized controlled trial" OR "cohort study" OR "RCT" OR "quantitative" OR "experimental".


• Qualitative-specific terms: "qualitative research" OR "interview" OR "focus group" OR "thematic analysis" OR "phenomenology".


• For mixed: "mixed methods" OR "convergent design" OR "embedded".


• Use operators: AND (narrows), OR (broadens), NOT (excludes, e.g., NOT "animal").


• Handle synonyms: Use truncation (e.g., qualitativ*) and proximity searching (e.g., "workplace NEAR/5 stress").


• Limits and Filters: Date range (e.g., 2000–present), language (e.g., English), peer-reviewed. Avoid method filters initially to prevent bias—screen abstracts manually.


• Tip: Create a search log (e.g., in Excel) tracking terms, databases, hits, and dates for reproducibility. Aim for 1,000–5,000 initial results depending on scope.

3. Execute and Document the Search

• Run Searches: Start with 2–3 core databases, then expand. Export results to EndNote, Zotero, or Mendeley for deduplication.


• Example PubMed Search (adapt to your topic):

("mindfulness"[MeSH Terms] OR mindfulness OR meditation) AND ("workplace"[MeSH Terms] OR employee OR occupational) AND (stress[MeSH Terms] OR burnout OR anxiety) AND (2000:2023[pdat])

• For qualitative subset: Add ("Qualitative Research"[MeSH Terms] OR qualitative OR interview OR "focus groups").


• Gray Literature and Hand-Searching:


• Include theses (ProQuest), conference abstracts (e.g., via Google Scholar alerts), policy reports (e.g., WHO, government sites), and preprints (medRxiv, SSRN).


• Hand-search key journals (e.g., Qualitative Health Research for qual; BMJ for quant) and reference lists of included studies (snowballing).


• Contact experts or authors for unpublished work.


• International Scope: Search non-English databases if relevant (e.g., LILACS for Latin America) and translate as needed.


• Time Estimate: 1–2 weeks for initial searches; involve a librarian for optimization.

4. Screen and Select Studies

• Deduplicate: Use software to remove ~20–30% duplicates.


• Screening Process (Two-Reviewer Rule for Rigor):


• Title/Abstract: Exclude obvious non-matches; aim for 10–20% full-text advancement.


• Full-Text: Assess against criteria—tag as quantitative, qualitative, or mixed.


• Resolve Disagreements: Discuss or use a third reviewer.


• PRISMA Flow Diagram: Document at each stage (e.g., records identified, screened, included).


• Challenges in Mixed Methods: Qualitative studies may be harder to find due to indexing biases—supplement with targeted qual databases.

5. Quality Appraisal and Synthesis

• While not directly your query, note for completeness:


• Quantitative: Use tools like ROBINS-I or AMSTAR.


• Qualitative: CASP or JBI checklists.


• Mixed: MMAT (Mixed Methods Appraisal Tool) for integrated assessment.


• Synthesis: Narrative for qual, meta-analysis for quant if possible; convergent synthesis for mixed (e.g., joint display of findings).

Common Pitfalls and Tips

• Bias Risk: Over-relying on quantitative databases misses qual depth—balance your strategy.


• Scope Creep: Pilot your search on a small scale to refine terms.


• Resources: Consult PRISMA-ScR extension for scoping/mixed reviews, or the JBI Manual for Evidence Synthesis. Tools like ASReview (AI-assisted screening) can speed things up.


• Ethics: Register your protocol on PROSPERO if health-related.