eTable. Definition and classification of evidence levels and recommendation grades.

Evidence level	Strength	Definition	Recommendation
1a	A	Meta-analyses. systematic _reviews of randomized controlled trials. megatrials	"Should"
1b		Randomized controlled trials
2a	B	Non-randomized studies. cohort studies with control groups	"Probably should"
2b	C	Observational studies _(case–control studies. cohort _studies)	"May"
3	D	Cross-sectional studies. _ecological studies. cohort studies without control group. case reports	GCP
4	X	Clinical experience	GCP

Classification according to tables of the AAP SCQIM (2 e2) and a DEGAM guideline (e3)

AAP SCQIM. American Academy of Pediatrics Steering Committee on Quality Improvement and Management; _DEGAM. German College of General Practitioners and Family Physicians; GCP. good clinical practice