Table 3 Levels of evidence according to the Oxford Center of Evidence-Based Medicine [7]
From: Consensus evidence-based clinical practice recommendations for the management of fibromyalgia
Level | Therapy/prevention, etiology/harm |
|---|---|
1a | SR (with homogeneity∗) of RCTs |
1b | Individual RCT (with narrow confidence interval) |
1c | All or none§ |
2a | SR (with homogeneity∗) of cohort studies |
2b | Individual cohort study (including low-quality RCT; e.g., < 80% follow-up) |
2c | “Outcomes” research; ecological studies |
3a | SR (with homogeneity∗) of case-control studies |
3b | Individual case-control study |
4 | Case series (and poor-quality cohort and case-control studies) |
5 | Expert opinion without an explicit critical appraisal or based on physiology, bench research, or “first principles” |