Table 1.

Grading scheme used to score the quality of experimental design for manuscripts included in this systematic review, modified from a grading system published by the Oxford Centre for Evidence-Based Medicine (30).

Experimental design grade (EDG)	Categories of therapeutic FCGS studies
I	Randomized, controlled, double-blinded prospective clinical trials
II	Prospective clinical trials (± control group)
III	Retrospective case series, n > 10; case–control study
IV	Retrospective case series, n < 10
V	Single patient case report; expert opinion