CLASSIFICATION OF EVIDENCE LEVELS

INTRODUCTIONIn 1976 the Canadian Task Force on Preventive Health Care (CTFPHC), who were the first to build and organize the levels of evidence and grades of recommendation for asymptomatic patients, indicating which were the most appropriate procedures and which should be avoided.

It is estimated that to date have been described and proposed various systems around 100 to assess the evidence.

CLASSIFICATION OF EVIDENCE LEVELS USED TODAY

Canadian Task Force on Preventive Health Care (CTFPHC)

Classification of evidence Sackett U.S. Preventive Services Task Force

(USPSTF) Centre for Evidence-Based Medicine,

Oxford (OCEBM) Scottish Intercollegiate Guidelines

Network (SIGN) National Institute for Health and Clinical

Excellence

1. CANADIAN TASK FORCE ON PREVENTIVE HEALTH CARE (CTFPHC)

The proposed classification of evidence seeks to generate recommendations in a practical way, by adopting a binary position, "do it or not", but only in the area of prevention.

LEVEL OF

EVIDENCE

I Randomized controlled

trial

II NO RANDOMIZED CLINICAL

EVALUATION1 Evidence obtiened from well

designed controlled trials with out randomization.

2 Evidence obtain from well designed COHORT OR CASE-

CONTROL, ANLITIC STUDIES, FREFARABLY FROM MORE THAN

ONE CENTER OR RESEARCH CENTER

3 multiple time serie with or without the intervention dramatic

resultus in uncontrolled experimetns also could be regarded

as this tipy of evidence.

IIIOpinions of respected authorities,

based on clinical experience, descriptive studies, or reports of

expert committees

2. CLASSIFICATION OF EVIDENCE SACKETT

This systematization proposed by epidemiologist David L. Sackett (which is generally used), the evidence hierarchy levels ranging from 1 to 5, with Level 1 the "best evidence" and level 5 the "worst, most evil or less good" according as want to read.

This was the first proposal considered other clinical scenarios or areas of different clinical practice of prevention. Incorporated economic analysis, diagnosis and prognosis.

3. U.S. PREVENTIVE SERVICES TASK FORCE (USPSTF) This nested panel and set the strength of their recommendations

from the quality of evidence and the net benefit, ie benefits minus harms of measure evaluated for application in "periodic health examinations." On the other hand, analyzed the cost-effectiveness of interventions, thus its contribution came to supplement what the group had generated CTFPHC

U.S. PREVENTIVE SERVICES TASK FORCE

4. CENTRE FOR EVIDENCE-BASED MEDICINE, OXFORD (OCEBM)

This proposal is characterized by assessing the evidence according to subject area or clinical setting and the type of study that involves the clinical problem in question.

Centre for Evidence based medicine, Oxford

5.SCOTTISHINTERCOLLEGIATEGUIDELINESNETWORK(SIGN)

This proposal originates as also having the subject focus of treatment. It differs from the previous ones by its particular emphasis on quantitative analysis involving systematic reviews and attaches importance to the reduction of systematic error.

LEVEL OF EVIDENCE

TYPE OF EVIDENCE

1 ++ High-quality meta-analyses, systematic reviews of RCTs, or RCTs with a very low risk of bias

1 +

Well-conducted meta-analyses, systematic reviews of RCTs, or RCTs with a low risk of bias

1 – Meta-analyses, systematic reviews of RCTs, or RCTs with a high risk of bias*

2 ++ High-quality systematic reviews of case–control or cohort studies High-quality case–control or cohort studies with a very low risk of confounding, bias or chance and a high probability that the relationship is causal

2 + Well-conducted case–control or cohort studies with a low risk of confounding, bias or chance and a moderate probability that the relationship is causal

2 – Case–control or cohort studies with a high risk of confounding bias, or chance and a significant risk that the relationship is not causal*

3 Non-analytic studies (for example, case reports, case series)

4 Expert opinion, formal consensus

*Studies with a level of evidence ‘–‘ should not be used as a basis for making a recommendation

Levels of evidence for intervention studies.

6. NATIONAL INSTITUTE FOR HEALTH AND CLINICAL EXCELLENCE (NICE)

This initiative comes from the National Health Service in the United Kingdom (NHS) covers the topic of therapy and diagnosis. Adapt the rating by SIGN for therapy and uses the diagnostic OCEBM, so that an assessment is made of the available evidence based on these tools.

GRADES OF RECOMMENDATION FROM THE SIGN (THERAPY)

BIBLIOGRAFÍA

http://www.eguidelines.co.uk/eguidelinesmain/gip/vol_6/aug_03/duncan_aug03.htm

http://www.nice.org.uk/niceMedia/pdf/GDM_Chapter7_0305.pdf

http://www.pccrp.org/docs/PCCRP%20Section%20I.pdf

http://www.nzda.org.nz/pub/resources/eb_levelsOfEvidence.pdf

http://www.eboncall.org/content/levels.html