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Table 1 Levels of CEBM modified for scientific papers investigating disease pathophysiology with bench research.

From: Systematic review with meta-analysis: cytokines in fibromyalgia syndrome

Level Differential diagnosis/symptom prevalence study Blinded Controls Remark/example
1a Systematic review of prospective cohort studies NR NR No systematic reviews available
1b Prospective cohort study with good follow-up NR Implicit An item is assessed (e.g. breast implant) and the occurrence of FMS is followed prospectively
1c All or none case series Test and assessment of results Obligatory All patients with low IL-4 have FMS, none has high IL-4
1d 1c Test or assessment of results Obligatory 1c
2a Systematic review (with homogeneity) of NR NR No systematic reviews available
  2b and better studies    
2b Retrospective cohort study, or poor follow-up NR Implicit FMS patients are investigated now, if they have had breast implants in the past; large size studies
2c Ecological studies Test and assessment of results Implicit FMS patients are investigated simultaneously, if they have FMS and if they have low IL-4 levels.
2d 2c Test or assessment of results Implicit 2c
3a Systematic review (with homogeneity) of 3b and better studies    No systematic reviews available
3b Non-consecutive cohort study, or very limited population Test and assessment of results Obligatory FMS patients and controls (limited population) are now investigated if they have low IL-4
     levels
3c 3b Test or assessment of results Obligatory 3b
3d 1c, 2c, 3b Not blinded Obligatory  
4 Case series or superseded reference standards   All studies without control group Case series with historical controls; case reports
5 Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles" NR   
  1. Abbreviations: CEMB: Oxford Center for Evidence-based Medicine FMS: fibromyalgia syndrome; NR: not relevant
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