Table 2.

Phenotypic domains and statistical methods used in the included studies

	Hypothesis-driven studies	Data-driven studies
	n = 8	n = 25
Number of phenotypic domains used for subtyping - N (%)
Single-domain	7 (87.5)	9 (36.0)
Two domains	1 (12.5)	-
> = 3 domains		16 (64.0)
Phenotypic domain(s) - N (%)
Demographic	2 (25.0)	8 (32.0)
Motor	3 (37.5)	18 (72.0)
Cognitive	1 (12.5)	17 (68.0)
Emotional	1 (12.5)	17 (68.0)
Autonomic	1 (12.5)	11 (44.0)
Treatment	-	3 (12.0)
Non-clinical Biomarkers*	-	5 (20.0)
*Imaging (n = 4), biochemical (n = 1)
Statistical approaches
Pre-determined groups	8 (100)	-
Hierarchical cluster analysis	-	7 (28.0)
Non-hierarchical cluster analysis	-	16 (64.0)
Hierarchical and Non-hierarchical cluster analysis		1 (4.0)
Other		1 (4.0)

Five studies were not included in this analysis for the following reasons: combined hypothesis- and data-driven approach (n = 2) and other methods (regression analyses, n = 2; subtype criteria defined post-hoc, n = 1).