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Report in English with a Dutch summary (KCE reports 45A)

Report in English with a Dutch summary (KCE reports 45A)

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190 Screen<strong>in</strong>g for Colorectal Cancer: Appendices <strong>KCE</strong> <strong>reports</strong> vol.45<br />

SIGN<br />

The Scottish Intercollegiate Guidel<strong>in</strong>es Network (SIGN 49) published (2001)<br />

concise rat<strong>in</strong>g schemes for appraisal of the strength of evidence given by<br />

reviewed scientific articles. Different grades of recommendation relate to the<br />

strength of the evidence on which they are based:<br />

I. Levels of Evidence:<br />

1 ++ : High quality meta-analyses, systematic reviews of<br />

randomised controlled trials (RCTs), or RCTs <strong>with</strong> a very low<br />

risk of bias<br />

1 + : Well-conducted meta-analyses, systematic reviews of RCTs,<br />

or RCTs <strong>with</strong> a low risk of bias<br />

1 : Meta-analyses, systematic reviews of RCTs, or RCTs <strong>with</strong> a<br />

high risk of bias<br />

2 ++ : High quality systematic reviews of case control or cohort<br />

studies or high quality case control or cohort studies <strong>with</strong> a very<br />

low risk of confound<strong>in</strong>g or bias and a high probability that the<br />

relationship is causal<br />

2+ : Well-conducted case control or cohort studies <strong>with</strong> a low<br />

risk of confound<strong>in</strong>g or bias and a moderate probability that the<br />

relationship is causal<br />

2 : Case control or cohort studies <strong>with</strong> a high risk of<br />

confound<strong>in</strong>g or bias and a significant risk that the relationship is<br />

not causal<br />

3 : Non-analytic studies, e.g. case <strong>reports</strong>, case series<br />

4 : Expert op<strong>in</strong>ion<br />

II. Grades of recommendation:<br />

The grade of recommendation relates to the strength of the evidence on which<br />

the recommendation is based. It does not reflect the cl<strong>in</strong>ical importance of the<br />

recommendation.<br />

A : At least one meta-analysis, systematic review of RCTs, or<br />

RCT rated as 1 ++ and directly applicable to the target population;<br />

or a body of evidence consist<strong>in</strong>g pr<strong>in</strong>cipally of studies rated as 1 +,<br />

directly applicable to the target population, and demonstrat<strong>in</strong>g<br />

overall consistency of results<br />

B : A body of evidence <strong>in</strong>clud<strong>in</strong>g studies rated as 2++ directly<br />

applicable to the target population, and demonstrat<strong>in</strong>g overall<br />

consistency of results; or extrapolated evidence from studies<br />

rated as 1++ or 1+<br />

C : A body of evidence <strong>in</strong>clud<strong>in</strong>g studies rated as 2+, directly<br />

applicable to the target population and demonstrat<strong>in</strong>g overall<br />

consistency of results; or extrapolated evidence from studies<br />

rated as 2++<br />

D : Evidence level 3 or 4; or extrapolated evidence from studies<br />

rated as 2+

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