J Neurol (2012) 259:1793–1800 Table 2 Mean HDQoL Speciﬁc and Summary Scale scores by rater HDQOLa Speciﬁc Scales Cognitive Hopes and Worries Services Physical and Functional Mood State Self and Vitality Summary Scale Mean (SD) 51.34 (32.24) 50.98 (27.93) 69.71 (34.57) 62.05 (33.56) 58.66 (28.08) 57.39 (25.78) 57.71 (25.03) CI conﬁdence interval, HDQoL Huntington’s disease health-related quality of life questionnaire a HDQOL scales are scored on a 0 (worst HrQoL) – 100 (best HrQoL) scale b A positive mean difference indicates that self-rated scale score is higher than proxy-rated scale score c Effect of rater (self vs. proxy) in 2-way mixed ANOVA, rater 9 HD Stage Self-rated (n = 105) Proxy-rated (n = 105) Mean (SD) Mean diffb 95% CI ANOVA rater effectc F(1,101) 46.52 (33.98) 56.89 (30.57) 72.37 (33.97) 59.97 (34.80) 57.42 (28.12) 53.60 (26.75) 56.2 (26.46) 4.82 -5.90 -2.65 2.08 1.24 3.78 1.50 0.74 to 8.90 -9.90 to -1.91 -7.74 to 2.43 -1.08 to 5.25 -2.77 to 5.24 0.21 to 7.35 -1.21 to 4.21 3.45 11.32 1.75 2.90 \1 2.22 \1 1797 p 0.07 0.001 ns 0.09 ns ns ns 100 reo90 c S80 x ed70 n I ry60 a m50 m u40 S ted30 -tra20 iten10 aP 0 y = 0.8073x + 12.336 = Early HD = Moderate HD = Advanced HD 0 10 20 30 40 50 60 70 80 Proxy-rated Summary Index Score 90 100 Fig. 2 Plot of patient-rated versus proxy-rated Summary Scale scores, with regression line and 95% CIs based on all data. Symbols represent patient’s stage of HD: bullet Early, shadowed white circle Moderate, ﬁlled diamond Advanced independent from the preceding one, because Moderate subgroup proxies were not more likely to be male than those in other subgroups, v2 \ 1. The excess of male proxies among outliers is not simply an extreme case of generally poor prediction of patient HrQoL by males; after removing all outliers, the absolute standardised residuals of male proxies were similar to those of females (male M = 0.68, female M = 0.65, t(95) \ 1). Scatterplots of other subscales (not shown) show the same pattern of lower proxy–patient agreement and more outliers in the moderate HD group. This is conﬁrmed by the ICCs, see Table 3. ICC values for the whole sample reﬂected excellent ([0.80) or substantial ([0.60) agreement on all scales, as did virtually all values for the Early and Advanced HD subgroups separately. In the Moderate HD subgroup, agreement was moderate (\0.60) to poor (\0.40). Agreement in the Advanced HD subgroup might have been inﬂated because Advanced HD patients were more likely than others to have reported that they received assistance from proxies in completing the questionnaires, (v2(2,N = 104) = 15.56, p \ 0.001). Therefore, ICCs were recomputed for the Advanced HD subgroup after removing the 16 cases (out of a total of 50) who received assistance. ICCs for this subset were slightly lower than for the whole Advanced subgroup—e.g. Summary Scale ICC = 0.71 compared to 0.81 for the whole subgroup—but agreement remained substantial on all scales except for Cognitive, and Self and Vitality, where it was moderate though still highly signiﬁcant. Discussion Previous reports on the carers of patients with HD have examined their reports of their own HrQoL and compared it to that of patients [27–29]. However, the current study using the proxy version of the HDQoL is the ﬁrst in which carers or others act as proxies, providing their own per- ceptions of the HrQoL of persons living with HD, main- taining a ‘proxy–proxy’ perspective [30]. Individual level correlations and group level analyses showed that patient–proxy agreement was substantial to excellent for the Summary Scale score of the HDQoL, and also for most of its Speciﬁc Scales. On the Speciﬁc Hopes and Worries Scale, proxies rated patients’ HrQoL as better than patients’ own ratings, while on both the Speciﬁc Cognitive Scale and Speciﬁc Physical and Functional Scale the reverse was true. The literature shows that for chroni- cally ill patients including those with neurological disor- ders such as stroke [31], brain cancer [32] and Parkinson’s disease [15, 16], patient–proxy agreement on validated 123