Guidelines to diagnose and treat peri-levator high-5 anal fistulas: Supralevator, suprasphincteric, extrasphincteric, high outersphincteric, and high intrarectal fistulas

Table 1 Levels of evidence for therapeutic studies[49]

Level		Type of evidence
1	A	Systematic review (with homogeneity) of RCTs
	B	Individual RCT (with narrow confidence intervals)
	C	All or none study
2	A	Systematic review (with homogeneity) of cohort studies
	B	Individual Cohort study (including low quality RCT, 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		Case series (and poor-quality cohort and case-control study
5		Expert opinion without explicit critical appraisal or based on physiology bench research or “first principles”

Citation: CEBM. OCEBM levels of evidence. [cited 11 January 2022]. Available from: https://www.cebm.ox.ac.uk/resources/levels-of-evidence/ocebm-levels-of-evidence. Copyright© 2022 University of Oxford.

RCTs: Randomized controlled trials.

Table 2 Grade practice recommendations¹

Grade	Level of Recommendation	Qualifying evidence	Implications for clinicians
A	Strong recommendation	Level I evidence or consistent findings from several studies of levels II, III, or IV	These recommendations should be followed unless an alternative approach with clear and compelling rationale is present
B	Recommendation	Consistent evidence of levels II, III, or IV	These recommendations should be followed but clinicians should understand that there is scope of improvement and these may be slightly modified as per patient preferences
C	Option	Levels II, III, or IV evidence, but findings are inconsistent	These guidelines are broad guidelines and clinicians should be flexible in their decision-making regarding appropriate practice keeping patient preferences in mind
D	Option	Level V evidence: Little or no substantial evidence	These recommendations may be referred but clinicians should consider all other available options while making decisions

¹Based on the American Society of Plastic Surgeons[34].