A clinimetric evaluation of the problem behaviors assessment short form (PBA-s) within the context of the Huntington's disease integrated staging system (HD-ISS).

BACKGROUND/OBJECTIVE This study extends prior clinimetric evaluations by examining the factor structure, internal consistency, and distributional properties of the Problem Behaviors Assessment - Short Form (PBA-s) in a large sample of people with Huntington's disease (pwHD) at various stages of progression using the Huntington's Disease Integrated Staging System (HD-ISS) framework. METHODS Baseline PBA-s item total scores were analyzed from 14,371 Enroll-HD participants. Using HD-ISS criteria, participants were categorized as Stage 0/1 (n = 3262; 23%), Stage 2 (n = 1722; 12%), or Stage 3 (n = 9387; 65%). RESULTS Missing responses were low across items and stages. Item total score distributions demonstrated significant skew in Stages 0/1 and 2. Within Stage 3, skewness was less prevalent but still present in most distributions. In all groups, the PBA-s demonstrated moderate internal consistency, though five items exhibited weak item-total correlations. Resultant factor structures differed from those previously reported and varied by HD-ISS stage. In Stages 0/1 and 2, a three-factor model representing internalizing, externalizing, and cognitive control problems accounted for 39-42% of the total variance. In Stage 3, a five-factor solution explained 56% of the overall variance and consisted of internalizing, externalizing, cognitive control problems, suicidality, and cognitive dysfunction. CONCLUSIONS While the PBA-s demonstrates adequate internal consistency, our results revealed high rates of non-endorsement (i.e., item total scores = 0) and a variable factor structure with disease progression. Thus, the PBA-s may not distinguish mild changes in behavioral symptoms that might occur in early HD-ISS stages of disease.