Poster 9: The Short Version of the Problem Behaviours Assessment for HD (PBA-s): An Item Response Analysis Using Data from the TRACK-HD Study

Background TRACK-HD is a multi-center, longitudinal study investigating a range of motor, cognitive, neuropsychiatric, and imaging measures as potential biomarkers for clinical trials in Huntington's disease (HD). Psychiatric assessments were conducted using a 10-item semi-structured interview, the short version of the Problem Behaviours Assessment for HD (PBA-s). To better characterize the relationship between scores on individual PBA items and overall severity of behavioral symptoms, a nonparametric item response analysis (Ramsay JO, Psychometrika 1991;56:611–630) was performed on the data from year 1 of the study. Methods The study included 366 subjects (123 affected, 123 premanifest gene carriers, 120 controls). Option Characteristic Curves (OCCs) were generated for all PBA-s items to determine the probability of scoring a particular option in relation to total PBA score. Results Most items, including Depressed Mood, Anxiety, Irritability, Aggressive Behavior, and Apathy showed generally good discriminative properties, but differences were observed between the three populations (affected, pre-manifest, and control subjects) in terms of their IRT curves. Suicidality was primarily endorsed at the higher levels of overall severity and did not discriminate well at lower PBA scores. A number of symptoms were rarely endorsed in this population at any level of overall behavioral symptom severity, including Delusions, Hallucinations and Disorientation. Conclusions These results demonstrate that some items on the PBA-s are more sensitive than others in capturing the overall severity of behavioral symptoms in early and pre-manifest HD, and thus may be more suitable to provide a reliable and valid measure of behavioral symptoms in this population.