From: A systematic review of intravenous gamma globulin for therapy of acute myocarditis
Level | Study design | |
---|---|---|
1 | A | Systematic review (with homogeneity) of randomized controlled trials |
 | B | Individual randomized controlled trial (with narrow confidence interval) |
 | C | All or none |
2 | A | Systematic review (with homogeneity) of cohort studies |
 | B | Individual cohort study (including low quality randomized controlled trial, e.g., < 80% follow-up) |
 | C | "Outcomes" research; ecological studies |
3 | A | Systematic review (with homogeneity) of case-control studies |
 | B | Individual case-control study |
4 | Â | Case series (and poor quality cohort and case-control studies) |
5 | Â | Expert opinion without explicit critical appraisal, or based on physiology, bench research or "first principles" |