Caregiver perspectives on meaningful change in the vineland adaptive behavior scales, second edition (VABS-II), in children with neuronopathic MPS II: an interview-based study

Background Neuronopathic mucopolysaccharidosis type II (MPS II; Hunter syndrome) is characterized by progressive multisystemic impacts, including cognitive impairment and behavioral problems. The Vineland Adaptive Behavior Scales, second edition (VABS-II) is recommended for assessing adaptive behavior in MPS II clinical studies; recently, an increase in VABS-II age-equivalent scores of 3 months (3AEq) has been defined as a threshold for improvement. The aim of the present study was to gain caregiver insights on what constitutes meaningful change on the VABS-II in response to treatment for children with neuronopathic MPS II. Ten semi-structured interviews were conducted with 11 caregivers of 11 children with neuronopathic MPS II aged 3–6 years old in the UK and USA. Caregivers were presented with hypothetical vignettes detailing changes in adaptive behavior and VABS-II scores in response to treatment over 1 year and were asked to select which one(s) represented a minimal meaningful change. The scores for the selected meaningful changes were then compared with those equivalent to an increase of 3AEq to assess the adequacy of this threshold. Caregivers discussed the rationale for their choices. Results For all nine VABS-II categories (feeding, drinking, undressing, dressing, brushing teeth and toileting [Personal Subdomain]; sharing skills [Interpersonal Relationships Subdomain]; Play and Leisure Subdomain; and Maladaptive Behavior Domain), the hypothetical vignette most commonly selected by caregivers as representing a minimal meaningful change was associated with the smallest change. The significant impact of small increases in independence and cognitive and physical abilities to perform daily activities were highlighted. For each functional activity within the Personal Subdomain, the majority of caregivers selected vignettes associated with changes in raw scores that were below the total Personal Subdomain raw score equivalent to a change of 3AEq. For sharing skills (Interpersonal Subdomain) and for the Play and Leisure Subdomain, the majority of caregivers chose vignettes associated with raw score changes that were below or equal, respectively, to raw scores associated with a change of 3AEq. Conclusions These insights from caregivers support the use of VABS-II for assessing adaptive behavior in children with neuronopathic MPS II and the use of 3AEq as a threshold for meaningful change.