What are the levels of evidence?
1) Systematic reviews and meta-analyses.
2) Randomised control trials.
3) Well-designed control trials.
4) Case control studies.
5) Systematic review of descriptive studies.
6) Descriptive cross-sectional studies.
7) Case report/ series.
What is the source of evidence of a systematic review or meta-analysis?
Evidence from a systematic review or meta-analysis of all relevant RCTs (randomised controlled trial) or evidence-based clinical practice guidelines based on systematic reviews of RCTs or three or more RCTs of good quality that have similar results.
What is the source of evidence of a randomised control trial?
Evidence obtained from at least one well-designed RCT (e.g. large multi-site RCT).
What is the source of evidence of a well-designed control trial?
Evidence obtained from well designed controlled trials without randomisation.
What is a case control study?
A study that compares patients who have a disease or outcome of interest (cases) with patients who do not have the disease or outcome (controls), and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group to determine the relationship between the risk factor and the disease.
Case control studies are observational because no intervention is attempted and no attempt is made to alter the course of the disease.
What is the source of evidence of a systematic review of descriptive studies?
Evidence from systematic reviews of descriptive or qualitative studies (meta-synthesis). Sometimes referred to as an ecological study.
What is the source of evidence of a descriptive cross-sectional study?
Evidence from a single descriptive or qualitative study.
What is the source of evidence of a case report/series?
Evidence from the opinion of authorities and/or reports of expert committees.
What is a meta-analysis?
A quantitative, formal, epidemiological study design used to systematically assess the results of previous research to derive conclusions about that body of research.
What is a systematic review?
A systematic review summarises the results of available carefully designed healthcare studies (controlled trials) and provides a high level of evidence on the effectiveness of healthcare interventions.
