Level I
Experimental study, randomized controlled trial (RCT)
Systematice review of RCTs, with or without meta-analysis
Level II
Quasi-experimental Study
Systematic review of a combination of RCTs and quasi-experimental, or quasi-experimental studies only, with or without meta-analysis.
Level III
Non-experimental study
Systematic review of a combination of RCTs, quasi-experimental and non-experimental, or non-experimental studies only, with or without meta-analysis.
Qualitative study or systematice review, with or without meta-analysis
Level IV
Opinion of respected authorities and/or nationally recognized expert committees/consensus panels based on scientific evidence.
Includes:
- Clinical practice guidelines
- Consensus panels
Level V
Based on experiential and non-research evidence.
Includes:
- Literature reviews
- Quality improvement, program or financial evaluation
- Case reports
- Opinion of nationally recognized expert(s) based on experiential evidence
These are some of the publication types that are associated with higher levels of evidence. You may want to start at the top of the pyramid and work your way down.
Publication Types by Question Type: Different study types are suited to different questions. For example:
Most Clinical Questions: Meta-analyses, systematic reviews
Therapy: Randomized Controlled Trial
Diagnosis: Prospective, blind controlled trial compared to gold standard
Prognosis: Cohort study, case control, case series/case report
Evidence-Based Practice (EBP): Evidence-based practice is the judicious use of the best research evidence (found in health sciences literature), clinical expertise (what the health care provider knows) and patient values (what the patient wants and believes) to create a plan of action regarding patient care. Evidence-based practice is an umbrella term that covers evidence-based medicine, evidence-based dentistry, evidence-based public health, evidence-based nursing and etc.
Healthcare professionals sometimes use the PICO or PICOT format to develop keywords for searching of clinical questions where:
P - Patient or Population or Problem
I - Intervention or prognostic factor of interest
C - Comparison to intervention
O - Outcome of interest
T - Time (sometimes included)
For more information about forming and using a PICO question to search, please see the American Journal of Nursing article below.
Stillwell, Susan B. DNP, RN, CNE; Fineout-Overholt, Ellen PhD, RN, FNAP, FAAN; Melnyk, Bernadette Mazurek PhD, RN, CPNP/PMHNP, FNAP, FAAN; Williamson, Kathleen M. PhD, RN. Evidence-Based Practice, Step by Step: Asking the Clinical Question: A Key Step in Evidence-Based Practice. AJN, American Journal of Nursing 110(3):p 58-61, March 2010. | DOI: 10.1097/01.NAJ.0000368959.11129.79