Classification and Clinical Diagnosis of Fibromyalgia Syndrome: Recommendations of Recent Evidence-Based Interdisciplinary Guidelines

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.