Levels of evidence
Encyclopedia
Levels of evidence is a ranking system used in evidence-based practices to describe the strength of the results measured in a clinical trial
or research study. The design of the study (such as a case report
for an individual patient or a double-blinded randomized controlled trial
) and the endpoints measured (such as survival or quality of life
) affect the strength of the evidence
. Levels of evidence range from I-V.
Ia - Evidence from Meta-anlysis of Randomised Controlled Trials
Ib - Evidence from at least one Randomised Controlled Trials
IIa - Evidence from at least one well designed controlled trial which is not randomised
IIb- Evidence from at least one well designed experimental trial
III - Evidence from case, correlation, and comparative studies.
IV - Evidence from a panel of experts
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
or research study. The design of the study (such as a case report
Case report
In medicine, a case report is a detailed report of the symptoms, signs, diagnosis, treatment, and follow-up of an individual patient. Case reports may contain a demographic profile of the patient, but usually describe an unusual or novel occurrence....
for an individual patient or a double-blinded randomized controlled trial
Randomized controlled trial
A randomized controlled trial is a type of scientific experiment - a form of clinical trial - most commonly used in testing the safety and efficacy or effectiveness of healthcare services or health technologies A randomized controlled trial (RCT) is a type of scientific experiment - a form of...
) and the endpoints measured (such as survival or quality of life
Quality of life
The term quality of life is used to evaluate the general well-being of individuals and societies. The term is used in a wide range of contexts, including the fields of international development, healthcare, and politics. Quality of life should not be confused with the concept of standard of...
) affect the strength of the evidence
Evidence
Evidence in its broadest sense includes everything that is used to determine or demonstrate the truth of an assertion. Giving or procuring evidence is the process of using those things that are either presumed to be true, or were themselves proven via evidence, to demonstrate an assertion's truth...
. Levels of evidence range from I-V.
Ia - Evidence from Meta-anlysis of Randomised Controlled Trials
Ib - Evidence from at least one Randomised Controlled Trials
IIa - Evidence from at least one well designed controlled trial which is not randomised
IIb- Evidence from at least one well designed experimental trial
III - Evidence from case, correlation, and comparative studies.
IV - Evidence from a panel of experts
External links
- Levels of evidence entry in the public domain NCI Dictionary of Cancer Terms
- Evidence and diagnostics
- EBM resources page, with a diagram showing different levels of evidence forming a pyramid