4. Lowest level of evidence - Studies:
Original research inc. all types of trials, Controlled Trials, Clinical Trials, Cohort studies etc.
Randomized Controlled Trials (RCTs) are the highest level of evidence in this group. However, they may not be the most appropriate study design to answer your clinical question. Sometimes an observational/qualitative study is required (e.g. a question about patient/professional experiences, values, attitudes). (Refer to Clinical question types page for a chart of question types and the best study designs for answering them).
The most important sources in the list below for EBP are the Cochrane Central Register of Controlled Trials, Medline, PubMed, and Scopus.
Health-specific sources of primary studies:
Clinical trial registries (useful for finding new, emerging evidence):