Table 3.
Comparison of the categorisation of evidence (treatment) and recommendations of the Canadian, German, and Israeli guidelines.
| Canada | Germany | Israel | |
|---|---|---|---|
| Evidence level I | SR of randomised controlled trials or n-of-1 trial* | Ia-SR (with homogenity) of RCTs** Ib-individual RCT (with narrow confidence Interval)** IC-all or none** |
SR of randomised controlled trials with large number of participants (over 1000) |
| Evidence level II | Randomized trial or (exceptionally) observational studies with dramatic effect* | IIa-SR (with homogeneity) of cohort studies** IIb-individual cohort study (including low quality RCT; e.g., <80% followup)** IIc-“Outcomes” research; Ecological studies** |
SR of observational studies, cohort studies, or small randomized studies |
| Evidence level III | Nonrandomized controlled cohort/follow-up study* | IIIa-SR (with homogenity) of case-control studies** IIIB-individual case-control study** |
Nonrandomized controlled studies |
| Evidence level IV | SR of case-control studies, historically controlled studies* | Case-series (and poor quality cohort and case-control studies)** | SR of case-control studies, open studies, and case reports |
| Evidence level V | Expert opinion | Expert opinion without explicit critical appraisal or based on physiology, bench research, or “first principles”** | Expert opinion |
| Recommendation strength A | Consistent level I studies | Directly based on evidence level I*** | “Strong evidence”: based on level I evidence |
| Recommendation strength B | Consistent level 2 or 3 studies or extrapolations from level 1 studies | Directly based on evidence level II or extrapolated recommendation evidence level I*** | “Medium evidence”: based on level II evidence |
| Recommendation strength C | Level 4 studies or extrapolations from level 2 or 3 studies | Directly based on evidence levels III, IV, and V*** | “Weak evidence”: based on levels III-IV evidence |
| Recommendation strength D | Level 5 evidence or troublingly inconsistent or inconclusive studies of any level | ||
| Panel consensus | Opinion supported by entire Canadian Fibromyalgia Guidelines Committee | Recommendation supported by majority of guideline group**** | Recommendation supported by entire Israeli fibromyalgia group panel |
RCT: randomised controlled trial; SR: systematic review or meta-analysis.
*Level may be graded down on the basis of study quality, imprecision, and indirectness, because of inconsistency between studies or because the absolute effect size is very small; level may be graded up if there is a large or very large effect size.
**Level may be graded down on the basis of study quantity (<4 RCTs of <200 patients), study quality (low study quality according to van Tulder score), low external validity (exclusion of patients with inflammatory rheumatic diseases and/or anxiety or depressive disorders), and evidence of publication bias.
***An up- or downgrading of recommendations is possible depending on the consistency of the results of the studies, the clinical relevance of the outcomes and effect sizes of the studies, the benefit-harm ratio, ethical considerations, patients' preferences, and the applicability of the therapies.
****The strength of consensus was classified as follows: strong consensus: consent of >95%, consensus: consent of 75–95%, majority consent: consent of 50–75%, and no consent: consent of <50% of the participants. A minority vote with a substantial rationale was possible.