Table 1 Selected studies and key study features

Calvert et al. [25] (2013)

UK

▪ Cross-sectional survey

▪ Recruited through disease charities, specialist neurology clinics at University Hospital Birmingham Trust and via the UK Clinical Research Networks

▪ Patients with HD (whether self-reported or confirmed diagnosis was not reported)

▪ Mean age: 57.1 years

▪ Male: 45.1%

▪ Mean no. of years since diagnosis: 4.9

Utility measure: EQ-5D index score (3L vs. 5L versions of EQ-5D not reported, value set not reported)

Carlozzi et al. [27] (2014)

US

▪ Cross-sectional surveys of patients with HD and their proxies (caregivers)

▪ Recruited through online panel and a display at 2012 HDSA annual meeting

▪ Patients’ characteristics (e.g., diagnoses, gene testing, years since diagnosis) and outcomes were self-reported

▪ Individuals with HD (self-reported) (n = 132)

▪ Caregivers (n = 40)

▪ Mean age: 40.8 years

▪ Female: 48%

▪ Mean no. of years since diagnosis: 4.8

Utility measure: EQ-5D index score (3L vs. 5L versions of EQ-5D not reported, value set not reported)

Other measures:

▪ HD-PRO-TRIAD

▪ Neuro-QOL

Carlozzi et al. [16] (2016)

Other articles based on the same study: Carlozzi et al. [13] (2015), Carlozzi et al. [14] (2018), Carlozzi et al. [15] (2019)

US

▪ Longitudinal, prospective, observational study

▪ Clinician-administered data collection (for clinical and demographic outcomes)

▪ Patient-reported assessments completed by patients (or with assistance from a family member or site staff)

▪ Recruitment from specialized treatment centers, other ongoing studies (e.g., Predict-HD), and the National Huntington Disease Roster and existing online medical record data capture systems

▪ Adults (aged ≥ 18 years) with prodromal and/or manifest HD, positive CAG test for gene expansion and/or clinical diagnosis (n = 536)

▪ Majority of prodromal patients were from the Predict-HD study

▪ Mean age: 48.74 years

▪ Female: 59.0%

▪ Mean (SD) no. of years since diagnosis (for nonprodromal patients): 3.97 (4.22)

Utility measure: EQ-5D index (3L vs. 5L versions of EQ-5D not reported, value set not reported)

Other measures:

▪ HDQLIFE, SF (new 4-item scale), PROMIS, Neuro-QOL

▪ WHODAS 2.0, RAND-12

Claassen et al.

[17] (2022)

Claassen et al. [47] (2021), abstract

US

▪ One-time computer-assisted phone interviews to estimate utilities for 4 severity levels of HD chorea described by vignettes

▪ Participants (n = 155) were general US public recruited by an online panel

▪ Mean age: 47 years

▪ Male: 48.4%

▪ Other measures:

▪ TTO

▪ EQ-5D VAS (normalized 0 to 1)

Dorey et al. [19] (2016)

Spain

▪ European HD burden survey (Euro-HDB)

▪ Cross-sectional survey

▪ Patients with a well-established diagnosis of HD and their caregivers

▪ Recruited with the help of a hospital neurologist

▪ Mean age: 49.66 years

▪ Male: 49.09%

▪ Derived mean no. of years since diagnosis: 5.54

Utility measure: EQ-5D-3L (value set not reported)

▪ Other measure included: Huntington Quality of Life Instrument (H-QoL-I)

Exuzides et al.

[21] (2022)

US

▪ A cross-sectional study based on survey data

▪ Primary data: a prospective, customized survey administered by the Rare Patient Voice (July 2019–August 2019)

▪ Control: a nationally representative online survey, National Health and Wellness Survey

▪ Patients’ characteristics and outcomes were self-reported

▪ HD patients and care partners reported their “own” HRQOL level (i.e., no proxy rating)

▪ Individuals with HD (self-reported diagnosis) between ages 18–70 years (n = 41; mean age: 45.61 years; 68.3% female)

▪ Matched general population (n = 123; mean age: 45.61 years; 68.3% female)

Utility measures:

▪ EQ-5D-5L Index (value set not reported)

▪ EQ-5D VAS

Other measure: PHQ-9

Hawton et al.

[23] (2019)

12 European countries

▪ A longitudinal, observational study from the European Huntington’s Disease Network (the REGISTRY study)

▪ Annual evaluations of demographic, clinical, and patient-reported outcomes conducted by the investigators

▪ Between annual visits, every 2 months, participants completed surveys on demographic, clinical, and patient-reported outcome measures

▪ Patients with HD in the REGISTRY study were clinically diagnosed

▪ Mean age: 48.6 years

▪ Female: 53%

▪ Mean duration since diagnosis: 4.5 years

▪ Utility measure: SF-6D

▪ Participant responses to SF-36 were converted to SF-6D–based utility values [34]

Hocaoglu et al.

[26] (2012)

UK

▪ Prospective cross-sectional survey

▪ HD patients recruited by mail-out via the HD association

▪ Subset of HRQOL survey

▪ Patient characteristics and outcomes were self-reported

▪ Persons with HD (n = 105)

▪ Self-reported diagnosis (87% reported having positive gene status, 67% reported having clinical diagnosis)

▪ Female: 58% (61/105)

▪ Mean age: 56.42 years

Utility measures:

▪ EQ-5D index (3L vs. 5L versions of EQ-5D not reported, value set not reported)

▪ EQ-5D VAS

Other measures:

▪ SF-12v2

▪ HDQoL

Quinn et al.

[20] (2016)

UK

Netherlands

Germany

Norway

▪ A single-blind, multi-center, randomized controlled trial to demonstrate the efficacy of a 12-week exercise program for patients with HD

▪ Trial sites = the ENROLL-HD/Registry sites

▪ All assessments were collected at the trial sites

▪ Patients with genetically confirmed diagnosis of HD

▪ Patients receiving routine HD clinical care or attending the ENROLL-HD study

▪ Control group (n = 15, males/females = 7/8, mean age: 51 years)

▪ Intervention group (n = 17, males/females = 9/8, mean age: 53 years)

Utility Measure: EQ-5D-3L (value set not reported)

Rodriguez Santana et al. [18] (2022),

Rodriguez Santana et al. [48] (2022), abstract

Germany, France, Italy, Spain, UK, US

▪ A retrospective analysis of the Huntington’s Disease Burden of Illness Study (HDBOI) cross-sectional dataset

▪ Demographic, clinical, and health care resource utilization reported by treating physicians

▪ HRQOL, nonmedical and indirect costs reported by patients and caregivers

▪ N = 336 patients with HD (8% [n = 27] by proxy for participants with a severe cognitive deficit, self-reported for the remainder of the sample)

▪ Mean age: 47.3 years

▪ Female: 35%

Utility Measures:

▪ EQ-5D-5L with England value set

▪ SF-6D

Shaw et al. [22] (2022)

Canada

▪ Cross-sectional online survey

▪ 3 types of participants: patients with HD, patient proxies (for patients who were unable to complete the survey), care partners

▪ Patient characteristics and outcomes were self- (or proxy-) reported

▪ 62 adult patients with self-reported diagnosis of HD

▪ A separate set of self-reported unpaid care partners identified as proxies of HD patients

▪ Mean age: 51.2 years

▪ Female: 28% (17/61)

Mean (SD) years since diagnosis: 9.9 (7.3)

Utility Measure: EQ-5D, mapped from the SF-36 (UK TTO value set)