Table I.

HD Diagnostic Criteria

Genetically Confirmed		NOT Genetically Confirmed
Presymptomatic	No clinical motor signs or symptoms (Motor DCL = 0 or 1) No cognitive signs or symptoms May or may not have changes in imaging, quantitative motor assessments, or biomarkers No symptomatic treatment indicated Disease-modifying treatment when safe and available	Clinically At-Risk
Prodromal HD	Subtle motor signs (Motor DCL = 2) AND/OR subtle cognitive signs or symptoms Apathy, depression or other behavioral changes related to HD may be present Usually changes in imaging and quantitative motor assessments May need symptomatic treatment Disease-modifying treatment appropriate	Clinically Prodromal HD
Manifest HD	Presence of clinical motor AND/OR cognitive signs and symptoms that have an impact on life Functional changes, eg, decrease in TFC Motor DCL = 3 or 4 (or Motor DCL of 2 if cognitive changes are significant AND there is evidence of progression) Symptomatic treatment appropriate Disease-modifying treatment appropriate	Clinically Manifest (requires Motor DCL = 4 and cognitive changes)

DCL = diagnostic confidence level; TFC = Total Functional Capacity scale