(A) C2010 Consensus Process for Levels of Evidence (LOE) for prognostic and retrospective studies
Retrospective (LOE P3)
Prospective (LOE P1)
Retrospective (LOE P3)
Prospective (LOE P1)
(B) Assessment of study quality based on the following factors:
(i) Was the sample of patients representative?
Yes
Yes
Yes
Yes
(ii) Were outcomes measured in the same (preferably blinded) objective way in both groups?
No
No
Yes
Yes
(iii) Were known confounders identified and appropriately controlled for?
Yes
Yes
No
Yes
(iv) Was followup of patients sufficiently long and complete (eg >80%)?
Yes
Yes
Yes
Yes
(C) Validity of study results (presence of all 4 factors = good; presence of above 3 factors = fair; presence of above 2 factors = poor; presence of above 1 or less factors = study should be excluded from further review)