HD-PRO-TRIAD (TM) Validation: A Patient-reported Instrument for the Symptom Triad of Huntington's Disease

Background: Few valid, disease-specific measures of health-related quality of life (HRQOL) capture the spectrum of symptoms associated with Huntington's disease (HD). The HD-PRO-TRIAD (TM) is a new, HD-specific, patient-reported outcome (PRO) instrument of the HD symptom triad (cognitive decline, emotional/behavioral dyscontrol, and motor dysfunction) designed for clinical research and practice. The objective was to validate the HD-PRO-TRIAD (TM) through a cross-sectional sample of individuals with HD and caregivers. Methods: Development of the HD-PRO-TRIAD (TM) has been described elsewhere. A total of 132 individuals with HD and 40 HD caregivers, comprising 29 dyads, participated in the cross-sectional psychometric validation of this instrument. Participants provided responses to the HD-PRO-TRIAD (TM) and other HRQOL and disease severity instruments (EuroQOL 5D, Short Form 12, Neuro-QOL Item Banks, PROMIS Global Health, and self-reported Unified Huntington's Disease Rating Scale Total Functional Capacity and Independence Scales). Internal consistency, construct validity, and patient-caregiver proxy consistency were evaluated. Results: Internal consistency of the three domains and overall HD-PRO-TRIAD (TM) instrument was supported by Cronbach's alpha values >= 0.94. Construct validity was supported by significant correlations between HD-PRO-TRIAD (TM) domain scores and other measures of the same domains (e.g., significant positive correlations between HD-PRO-TRIAD (TM) Anxiety with Neuro-QOL Anxiety), as well as slightly weaker but still strong correlations with other HRQOL instruments (e.g., HD-PRO-TRIAD (TM) Anxiety and UHDRS Independence; all p < 0.01). Consistency between patient self-report and caregiver proxy report was supported by an intra-class correlation coefficient >= 0.92 for all three domains and the overall instrument. Discussion: These data indicate that HD-PRO-TRIAD (TM) is a reliable and valid HRQOL instrument that captures the typical triad of HD symptoms.