Table 1.

Minimal dataset

Item	Description	Justification
Identifier	Unique identifier, such as EUPID (https://eupid.eu)	Prevention of duplicate registration of patients Preservation of the possibility for re-identification by a trusted third party Facilitation of creating merged, datasets for secondary use (https://eupid.eu)
Participation in previous study/registry	Acronym of previous study/registry Identifier of participant	Facilitation of merging data from different studies/cohorts
Core demographic data	Sex, age, age at ataxia onset	Essential information for characterization of participants
Genetic information	Information on pathogenic and likely pathogenic genetic variant Information on performed tests and negative results	Essential information for stratification of participants
Disability status	Friedreich Ataxia Rating Scale (FARS) functional staging for ataxia (FARS part I)	Staging system providing a finer gradation compared to other systems
Patient’s global impression of change (PGI)	7-point Likert scale related to functional impairment due to ataxia compared to the situation one year ago	Highly relevant, patient-derived information on the disease course
Scale for the Rating and Assessment of Ataxia (SARA)	Scale for the Rating and Assessment of Ataxia (SARA)	SARA is the most widely used ataxia scale with a large amount of available data