Investigating clinical heterogeneity in systematic reviews: a methodologic review of guidance in the literature

Table 1 Descriptive characteristics of included resources that reported recommendations for investigating clinical heterogeneity in systematic reviews of controlled clinical trials (N = 101)

Descriptive Characteristics		N¹
Type of publication	Statistical paper	44
	Narrative review or expert opinion	29
	Methodological review	14
	Consensus-based guideline	9
	Textbook	5
Decade of publication	2000s	70
	1990s	27
	1980s	4
Guidance on statistical methods		75
Clinical variables (general ² or specific) recommended		39
Process for choosing clinical variables recommended		28

1. The number (N) of resources equals the percentage of resources since we include 101 total resources.
2. The term “general” means that the resource listed the term “patient”, “intervention”, or “outcome” as a category from which to consider covariates without suggesting specific variables.

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