Table 2.

Classification of different types of evidence and respective criteria

Type of evidence—abbreviation	Criteria
META	Evidence from >1 high-quality RCT Metaanalyses of high-quality RCTs
RAND	Evidence from 1 high-quality RCT Evidence from >1 moderate-quality RCT Metaanalyses of moderate-quality RCTs
OBS	Observational studies or registries Metaanalyses of such studies
OPN	Randomized, non-randomized, observational or registry studies with limitations of design or execution, case series Metaanalyses of such studies Physiological or mechanistic studies in human subjects Consensus of expert opinion based on clinical experience

RCT, randomized clinical trial.