Table 3.

Comparison of the new concept of “expected heterogeneity” (as used in the QoE-SPEO approach) to the concepts of “heterogeneity” and “inconsistency” (as used in the GRADE approach).

Concept	Definition	Relevant study types
Expected heterogeneity	Real and non-spurious heterogeneity (i.e., variability) that can be expected in the prevalence of exposure, within or between individual persons, because exposure to the risk factor may change over space and/or time	Studies of the prevalence of exposure to a risk factor
Heterogeneity	A broad term that can be used to describe any kind of variability among studies in a systematic review (Higgins et al. 2021)	All study types may display heterogeneity
Inconsistency	Differences in relative effect sizes across subgroups. Large inconsistency requires a search for an explanation (“explained heterogeneity”) (Guyatt et al. 2011)	Studies of the effect of an exposure on an outcome