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Consensus Statements 2008
Karolinska Stroke Update Consensus Statements 2008
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About Levels of Evidence Classification (from 2008)*
Classification of Evidence for a diagnostic measures:
Class I
A prospective study in a broad spectrum of persons with the suspected condition, using a ‘gold standard’ for case definition, where the test is applied in a blinded evaluation, and enabling the assessment of appropriate tests of diagnostic accuracy
Class II
A prospective study of a narrow spectrum of persons with the suspected condition, or a well-designed retrospective study of a broad spectrum of persons with an established condition (by ‘gold standard’) compared to a broad spectrum of controls, where test is applied in a blinded evaluation, and enabling the assessment of appropriate tests of diagnostic accuracy
Class III
Evidence provided by a retrospective study where either persons with the established condition or controls are of a narrow spectrum, and where test is applied in a blinded evaluation
Class IV
Evidence from uncontrolled studies, case series, case reports, or expert opinion
Classification of Evidence for a therapeutic intervention:
Class I
An adequately powered, prospective, randomized, controlled clinical trial with masked outcome assessment in a representative population or an adequately powered systematic review of prospective randomized controlled clinical trials with masked outcome assessment in representative populations. The following are required:
a.
randomization concealment
b.
primary outcome(s) is/are clearly defined
c.
exclusion/inclusion criteria are clearly defined
d.
adequate accounting for dropouts and crossovers with numbers sufficiently low to have a minimal potential for bias; and
e.
relevant baseline characteristics are presented and substantially equivalent among treatment groups or there is appropriate statistical adjustment for differences
Class II
Prospective matched-group cohort study in a representative population with masked outcome assessment that meets a-e above or a randomized, controlled trial in a representative population that lacks one criterion a-e
Class III
All other controlled trials (including well-defined natural history controls or patients serving as own controls) in a representative population, where outcome assessment is independent of patient treatment
Class IV
Evidence from uncontrolled studies, case series, case reports, or expert opinion
Definitions for levels of recommendation:
Level A
Established as useful/predictive or not useful/predictive for a diagnostic measure or established as effective, ineffective or harmful for a therapeutic intervention; requires at least one convincing Class I study or at least two consistent, convincing Class II studies.
Level B
Established as useful/predictive or not useful/predictive for a diagnostic measure or established as effective, ineffective or harmful for a therapeutic intervention; requires at least one convincing Class II study or overwhelming Class III evidence.
Level C
Established as useful/predictive or not useful/predictive for a diagnostic measure or established as effective, ineffective or harmful for a therapeutic intervention; requires at least two Class III studies.
Good Clinical Practice (GCP) points
Recommended best practice based on the experience of the guideline development group. Usually based on Class IV evidence indicating large clinical uncertainty, such GCP points can be useful for health workers
* Reference: Brainin M, Barnes M, Baron JC, Gilhus NE, Hughes R, Selmaj K, Waldemar G: Guidance for the preparation of neurological management guidelines by EFNS scientific task forces--revised recommendations 2004. Eur J Neurol 2004;11:577-581.
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