Table 2 Selected studies’ key study design features, population characteristics, and utility estimates

Calvert et al. [25] (2013, UK)

Cross-sectional survey of patients with rare, long-term neurological conditions

Not reported

Mean no. of years since diagnosis: 4.9

▪ EQ-5D index score, mean (95% confidence interval)

 • Overall: 0.30 (0.41 − 0.19), n = 22

Note: patients were allowed to receive “some help” by carers in responding to questions, but no proxy-reported utility scores were reported

Carlozzi et al. [27] (2014, US)

A cross-sectional survey of patients with HD and their proxies (caregivers)

Staging not reported

▪ Mean (SD) years since diagnosis: 4.8 (3.9)

▪ Mean (SD) years with motor symptoms: 5.7 (5.6)

▪ Mean (SD) years with any symptoms: 5.0 (3.5) (caregivers report: 5.7 [4.3])

▪ Mean (SD) TFC: 6.8 (4.3)

▪ Mean (SD) UHDRS IS: 3.5 (2.3)

▪ EQ-5D index score, mean (SD)

 • Self: 0.6 (0.3), n = 132

 • Proxy: 0.6 (0.3), n = 40

Note: the mean proxy-reported TFC (5.4) was lower than the mean self-reported mean TFC (6.8)

Carlozzi et al. [16] (2016, US)

Prospective, observational study (self-reported only)

▪ Prodromal HD (TFC 13), n = 205 (38.5%)

▪ Early-stage HD (TFC 7–13), n = 202 (38.0%)

▪ Late-stage HD (TFC 0–6), n = 125 (23.5%)

▪ TFC = clinician rated

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

 • Early-stage HD: 3.07 (3.71)

 • Late-stage HD: 5.88 (4.62)

▪ Mean (SD) UHDRS IS score:

 • All: 84.30 (16.62)

 • Prodromal HD: 97.71 (5.95)

 • Early-stage HD: 85.02 (9.65)

 • Late-stage HD: 61.40 (12.13)

▪ EQ-5D index score, mean (SD)

 • Prodromal HD: 0.89 (0.12): n = 205

 • Early-stage HD (TFC: 13 − 7): 0.80 (0.14); n = 202

 • Late-stage HD (TFC: 6 − 0): 0.71 (0.17); n = 125

 • All: 0.81 (0.15)

▪ Prodromal HD: positive CAG test for gene expansion but no symptoms

Claassen et al. [17]

(2022, US)

Vignettes (health state descriptions) valued by members of the US general population using time trade-off methods

Vignette descriptions of chorea severity:

(mild, mild/moderate, moderate/severe, severe)

NA

▪ TTO score, mean (SD)

 • Mild chorea, 0.64 (0.41)

 • Mild/moderate chorea, 0.48 (0.47)

 • Moderate/severe chorea, 0.26 (0.50)

 • Severe chorea, 0.07 (0.52)

▪ VAS (divided by 100): all, EQ-5D VAS: 0.79 (0.16)

 • Mild chorea, 0.59 (0.20)

 • Mild/moderate chorea, 0.47 (0.20)

 • Moderate/severe chorea, 0.32 (0.19)

 • Severe chorea, 0.19 (0.17)

Dorey et al. [19] (2016, Spain)

Cross-sectional self-reported survey

Overall severity level distribution was not reported, but the study included patients with low to high severity levels (UHDRS IS score of 10–60,70–80, 90–100)

Mean no. of years since diagnosis: 5.54

Mean functional score (0–7) in Huntington clinical self-reported instrument (H-CSRI): 3.06 (2.53)

▪ EQ-5D-3L index score, mean (SD)

 • Overall: 0.54 (0.43), n = 55

 • Low independence; UHDRS IS score ≤ 60 (high level of severity): 0.25 (mean)

 • High independence; UHDRS IS score > 80 (moderate or better severity): 0.84 (mean)

Exuzides et al. [21] (2022, US)

A cross-sectional study based on survey data

▪ HD patients

 • Early-stage: 48.8%

 • Mid-stage: 39.0%

 • Late-stage: 12.2%

Staging definition not reported

HD care partners were recruited but reported their “own” HRQOL level (i.e., no proxy rating)

▪ EQ-5D-5L, mean (SD)

 • All HD patients: 0.66 (0.21), n = 41

 • Matched general population for patients: 0.81 (0.17)

 • HD caregivers: 0.82

 • Matched general population for caregivers: 0.84

▪ EQ-5D VAS, mean (SD)

 • All HD patients: 58.83 (23.43)

 • Matched general population: 75.68 (21.00)

 • HD caregivers: 73.71

 • Matched general population for caregivers: 77.32

Hawton et al. [23] (2019, Europe)

A longitudinal, observational study

▪ TFC 13 − 11, n = 2,869

▪ TFC 10 − 7, n = 1,755

▪ TFC 6 − 3, n = 1,500

▪ TFC 2 − 0, n = 774

TFC = patient rated

▪ Years since diagnosis

 • < 1, n = 1,323

 • 1–4, n = 2,255

 • 5–9, n = 1,388

 • ≥ 10, n = 449

▪ Mean years since diagnosis: 4.5

▪ SF-6D utilities by stage, mean (SD)

 • TFC 13 − 11: 0.767 (0.131), n = 4,991

 • TFC 10 − 7: 0.675 (0.128), n = 2,753

 • TFC 6 − 3: 0.633 (0.121), n = 2,282

 • TFC 2 − 0: 0.575 (0.118) n = 774

▪ SF-6D utilities by years since diagnosis, mean (SD)

 • < 1: 0.691 (0.140)

 • 1–4: 0.683 (0.135)

 • 5–9: 0.659 (0.133)

 • ≥ 10: 0.640 (0.128)

Hocaoglu et al. [26] (2012, UK)

Prospective survey study

▪ At risk, n = 10

▪ Gene positive, n = 17

▪ Stages

 • Early, n = 9

 • Moderate, n = 18

 • Advanced, n = 50

NA

▪ EQ-5D index utilities, mean (SD)

 • Self-report: 0.56 (0.35), n = 105

▪ EQ-5D VAS scores, mean (SD)

 • Self-report: 58.38 (23.2)

Quinn et al. [20] (2016, searched by hand, Europe)

Randomized controlled trial evaluating the benefits of exercise in patients with HD

▪ TFC, mean (SD)

 • 9 (3) in control arm

 • 8 (3) in active arm

▪ UHDRS TMS, mean (SD)

 • 32 (14) (control)

 • 39 (22) (active)

▪ UHDRS SDMT, mean (SD)

 • 28 (10) (control)

 • 23 (9) (active)

▪ EQ-5D-3L index at baseline, mean (SD)

 • Control, index: 0.74 (0.17), n = 15

 • Intervention, index: 0.77 (0.19)

▪ EQ-5D index postintervention (13 weeks of exercise), mean (SD)

 • Control, index: 0.75 (0.19)

 • Intervention, index: 0.81 (0.14)

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

Retrospective analysis of the HDBOI dataset

▪ n = 336 for EQ-5D respondents

 • Early stage (TFC 13 − 7): 38%

 • Mid stage (TFC 6 − 4): 35%

 • Advanced stage (TFC 3 − 0): 26%

TFC was clinician rated

▪ N = 482 for SF-6D respondents

▪ Clinically diagnosed with symptomatic motor HD disease ≥ 12 months before study recruitment

▪ EQ-5D-5L utility estimates (all participants / self-reported / proxy reported), mean (SD)

 • Early-stage HD: 0.72 (0.22) / 0.74 (0.19) / 0.34 (0.31), n = 129/122/7

 • Mid-stage HD: 0.62 (0.18) / 0.62 (0.18) / 0.66 (0.26), n = 119/115/4

 • Advanced-stage HD: 0.37 (0.30) / 0.42 (0.27) / 0.13 (0.31), n = 88/72/16

▪ SF-6D utility estimates (all participants / self-reported / proxy reported), mean (SD)

 • Early-stage: 0.61 (0.12) / 0.61 (0.11) / 0.54 (0.11)

 • Mid-stage: 0.56 (0.07) / 0.56 (0.07) / 0.55 (0.06)

 • Advanced-stage: 0.50 (0.08) / 0.51 (0.08) / 0.44 (0.09)

▪ Staging based on Wild and Tabrizi [36] descriptors

 • Early-stage: TFC 13 − 7

 • Moderate-stage: TFC 6 − 4

 • Advanced-stage: TFC 3 − 0

Shaw et al. [22] (2022,

Canada)

A cross-sectional online survey

▪ TFC 13 − 11, n = 22

▪ TFC 7–10, n = 13

▪ TFC 6 − 3, n = < 10

▪ TFC 2 − 0, n = < 10

▪ No score, n = 10

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

▪ 42.4% experienced motor symptom onset

▪ EQ-5D mapped from SF-36 (UK TTO value set), all participants (n = 48)

• Mean (SD): 0.72 (0.24), n = 48

• Median: 0.77