Find the Evidence
For most types of clinical questions, a well-done systematic review or meta-analysis of all available studies is the best level of evidence.
The following list outlines the best study methodologies to answer different clinical questions
Type of question |
Ideal type of study |
Therapy |
Randomised control trial (RCT) |
Prevention |
RCT | Cohort Study | Case Control |
Diagnosis |
Prospective, blind controlled trial comparison to gold standard |
Prognosis |
Cohort study | Case Control | Case series or Case report |
Etiology/Harm |
RCT | Cohort study | Case control |
Cost analysis |
Economic analysis |
Once you identify the study type that will best answer your PICO question, plan your search. A good search strategy should include advanced search syntax and alternative search terms. Use resources containing pre-appraised evidence, where the information you find in these have already undergone a filtering and critical appraisal process.
The Evidence Pyramid below shows the levels of evidence that can be used to answer your question and along side the appropriate Library databases available to search for your results.
This pyramid shows the reliability of Primary and Secondary Research within the evidence hierarchy. When searching for evidence you should search for evidence at the highest level and progressively work down the pyramid if higher levels do not exist. Critical appraisal is required for all studies used at the Primary Research Level
Conducting the Search.
Health Librarians are highly skilled in assisting you with a search strategy and using the databases to retrieve valid results. For further assistance please . Alternatively our contact usTutorials help page provides links to tutorials for all the databases found on our website.
Upcoming Training Workshop
Finding the Evidence
Finding the Evidence for Guidelines and Policies
Meta Analysis and Systematic Reviews |
Clinical Trials (Randomised and non Randomised) |
Cohort Study |
Case Control Study |
Case Series |
Cross-sectional Study |
Additional Reading |