The first analysis was based on N = 730 prodromal individuals with at least 1 year and up to 7 years of follow-up data. These were participants who tested positive for the HD mutation, but did not have motor features indicating onset of diagnosable HD at the time of enrollment. Participants were seen yearly by clinicians experienced in the evaluation of movement disorders and specifically trained in administration of the Unified Huntington’s Disease Rating Scale (UHDRS) for PREDICT-HD [Huntington Study Group, 1996 (link)]. Of the 730 prodromal individuals, 137 received a HD diagnosis over the course of the study.
All aspects of the study were approved by the Institutional Review Board at each participating institution, and all aspects of the study are in compliance with the Declaration of Helsinki.
In accordance with clinical practice, diagnosis was made on the basis of “an otherwise unexplained characteristic movement disorder,” operationally defined as a score of 4 on the HD Diagnostic Rating Scale of the UHDRS. A rating of 4 indicates that the clinician had ≥ 99% certainty that the participant showed “unequivocal presence of an otherwise unexplained extrapyramidal movement disorder.” This method of diagnosis is “standard” in the respect of being approved by authorities such the Huntington Study Group (HSG)[Huntington Study Group, 1996 (link)]. Participants were excluded from the analysis if they received a rating of 4 at baseline.
Portions of the second analysis added 233 control participants, for a total sample size of N = 963. The control participants were offspring of at least one HD-diagnosed parent, but tested negative for the HD mutation (CAG repeat length < 36). Additional information about the participants and the PREDICT-HD study can be found in [Duff et al., 2010a (link); Nopoulos et al., 2011 (link); Paulsen et al., 2010b (link); Stout et al., 2011 (link)].
All aspects of the study were approved by the Institutional Review Board at each participating institution, and all aspects of the study are in compliance with the Declaration of Helsinki.
In accordance with clinical practice, diagnosis was made on the basis of “an otherwise unexplained characteristic movement disorder,” operationally defined as a score of 4 on the HD Diagnostic Rating Scale of the UHDRS. A rating of 4 indicates that the clinician had ≥ 99% certainty that the participant showed “unequivocal presence of an otherwise unexplained extrapyramidal movement disorder.” This method of diagnosis is “standard” in the respect of being approved by authorities such the Huntington Study Group (HSG)[Huntington Study Group, 1996 (link)]. Participants were excluded from the analysis if they received a rating of 4 at baseline.
Portions of the second analysis added 233 control participants, for a total sample size of N = 963. The control participants were offspring of at least one HD-diagnosed parent, but tested negative for the HD mutation (CAG repeat length < 36). Additional information about the participants and the PREDICT-HD study can be found in [Duff et al., 2010a (link); Nopoulos et al., 2011 (link); Paulsen et al., 2010b (link); Stout et al., 2011 (link)].
