1794 [9–11] and functional impairments [12], persons living with HD may experience difﬁculties with insight [13] and may display a lack of awareness [14]. For these reasons, proxy reports in certain instances could be the only point of reference available, as the person might be unable to report their HrQoL or complete a questionnaire due to various impairments caused by HD. Studies have attempted to establish patient–proxy agreement in evaluating HrQoL in other neurodegenerative conditions such as Alzheimer’s disease (AD) and Parkin- son’s disease (PD) [15–17]. Previous research with diseases such as AD also addressed variability of patient insight across different functional domains [18, 19] in order to better understand barriers to self-report [20]. The purpose of the current study was to examine patient and proxy ratings of HrQoL of persons at different stages of HD using the Hun- tington’s disease health-related quality of life questionnaire (HDQoL) and to examine factors that may affect proxy ratings. Proxies separately rated their own HrQoL using generic instruments, to determine whether a proxy’s own health status affects their judgement of a patient’s HrQoL. Methods Participants Persons living with HD who participated in this study were a subset of a larger validation sample for the HDQoL [21]. All were recruited through a mail-out via the Huntington’s Disease Association (HDA) in the UK and provided their consent prior to their inclusion in the study. From this sample, 105 persons living with HD chose to provide proxy data in addition to their own (At risk, n = 10; Pre-symp- tomatic gene positive, n = 17; Stage 1, n = 9; Stage 2, n = 8; Stage 3, n = 10; Stage 4, n = 35 and Stage 5, n = 15). The study was approved by University of Reading Research Ethics Committee and has been performed in accordance with 1964 Declaration of Helsinki. Procedure and measures Research questionnaires were sent to persons living with HD, referred to generically as patients although this includes people who were not yet clinically symptomatic. Those who volunteered to participate were invited to give the accompanying proxy report questionnaires to someone they felt knew them well. Patients were instructed that they might get assistance in completing the questionnaire, from the proxy or another helper, if they found this difﬁcult; however the questionnaire responses should be solely their own. Proxies were instructed to complete the questionnaires independently of the patient, and were asked to focus on 123 J Neurol (2012) 259:1793–1800 how they think the quality of life of the patient has been affected, drawing upon their perceptions and thoughts as a companion/carer. Patients and proxies were requested to return the questionnaires using the pre-paid reply envelope provided within a fortnight. Patients and proxies were asked to provide demographic details and information regarding patient’s functional ability as an indication of disease stage. They were asked to complete three questionnaires as follows. 1. Self- or proxy-report version, respectively, of the HDQoL [21]. This is a disease-speciﬁc patient reported outcome measure developed from HD patient inter- views, where each item comprises a relevant aspect of health-related quality of life on which HD participants provide a self-reported response on a Likert scale. The proxy-report version is identical to the self-reported patient version, except that proxies are asked their own opinion of the patient for each item. Following exploratory factor analysis and Rasch analysis of data from a larger sample, reported elsewhere [21], several scales can be identiﬁed. In the present paper, we report the Summary Scale and the six Speciﬁc Scales (i.e. Speciﬁc Cognitive, Speciﬁc Hopes and Worries, Spe- ciﬁc Services, Speciﬁc Physical and Functional, Spe- ciﬁc Mood State, Speciﬁc Self and Vitality) in order that proxy–patient agreement can be assessed both globally and selectively. Each Speciﬁc Scale total, and the Summary Scale, ranges from 0 (worst HrQoL) to 100 (best HrQoL). 2. Self-report version of the EQ-5D: note that proxies were here reporting their own health status, not the patient’s. This generic HrQoL measure comprises ﬁve questions on mobility, self-care, pain, usual activities and psychological status using three-point scales, and generates a Summary Scale (1 = Best Health State) and visual analogue scale to indicate general health status (100 = Best Health Status) [22]. 3. Self-report version of the SF-12v2: again, proxies reported their own status. This generic measure includes twelve items, measures eight domains of health on ﬁve-point scales, and is used to calculate two component scores—the Physical Component Summary Score (PCS) and the Mental Component Summary Score (MCS) [23]. PCS and MCS scales are trans- formed to 0–100 scale (0 = Worst, 100 = Best). Data analyses All statistical tests are designated signiﬁcant at p \ 0.05, two-tailed. Self and proxy agreement on the level of Speciﬁc and Summary Scale scores was examined by computing mean