MeSH is the controlled thesaurus managed by the NLM, primarily for PubMed article indexing, but useful in identifying keywords and developing keyword search strategies across other bibliographic databases.
Critical Appraisal Skills Programme - CASP 
There are a range of resources from CASP to support critical appraisal across a range of studies and research methods, including a series of checklists for a range of research types - CASP checklists.
Population | Intervention | Comparison | Outcome
is a framework and one of the CASP tools that can be used to break down clinical questions into keywords to develop a literature search strategy and critically appraise research hypotheses or research questions. It is for quantitative studies.
There are variations expanding this tool including PICOS - Study Design.
Population/Patient/Problem | Intervention | Comparison | Outcome | Context
CASP tool expanding on PICO with the addition of 'Context', useful for service evaluations and improvements.
Population | Exposure | Comparison | Outcome
CASP tool for qualitative questions focusing on and unintentional occurrence 'Exposure' instead of 'Intervention'.
Setting | Population/Perspective | Intervention | Comparison | Evaluation
CASP tool focusing on qualitative questions or experiences.
Condition | Context | Population
CASP tool to develop questions investigating the prevalence of a a condition, disease, problem or symptom.
Population | Exposure | Outcome
This tool was developed for the analysis of qualitative data to explore themes and experiences. For a comparison of the PICO and PEO tools see 'Clinical question PICO and PEO Research'.
Population/Participants | Concept | Context
Developed as a more flexible framework for scoping reviews by Arksey and O'Malley (2005), compared to the variety of frameworks developed for more focused systematic review questions. Developed further by and the recommended framework for scoping reviews by JBI.
Sample | Phenomenon of Interest | Design | Evaluation | Research type
Another development of and alternative to PICO, for qualitative and mixed-methods research, as a search development tool and critical appraisal tool.
Expectation | Client group | Location | Impact | Professionals | Service
A tool for use with qualitative studies looking at policies or services.
Previously known as CLIP - Client group | Location | Improvement / Innovation / Professionals.
More tools and frameworks
A useful table listing additional evaluation and search development tools/frameworks that are variations or developments of the above, or alternative frameworks are available through the University of Maryland LibGuide.
