Background Because of its centrality in the conceptualization of intellectual disability, reliable and valid measurement of adaptive behaviour is important to both research and clinical practice. The manual of the Vineland Adaptive Behavior Scales, recently released in its third edition, provides limited reliability information obtained from a sample composed primarily of typically developing individuals. The goal of this study was to evaluate the concordance of the Vineland-3 with the Vineland-II in a sample more similar in ability level to those in which the Vineland is commonly used. Methods Both editions of the Vineland Interviews were conducted with a convenience sample of 106 parents/caregivers of individuals with neurodevelopmental disability, participating at two neurodevelopmental disorder research clinics. Administrations were up to 7 days apart, but most (90%) were simultaneous. The concordance correlation coefficient (CCC) (95% confidence interval) and mean differences (95% confidence interval) were calculated for domain standard scores and subdomain v-scale scores. Results Domain-level CCC ranged from 0.78 [0.70, 0.84] (Communication) to 0.86 [0.76, 0.92] (Motor). Subdomain CCC ranged from 0.71 [0.62, 0.78] (Receptive Language) to 0.91 [0.85, 0.95] (Fine Motor). Vineland-3 scores were lower than Vineland-II scores; 77% of participants had lower Adaptive Behavior Composite scores on the Vineland-3 than on the Vineland-II. For the subdomains, the magnitude of this difference depended upon the level of adaptive behaviour. For Communication, the domain with the lowest CCC, the mean difference ranged from À13.70 [À8.03, À19.35] for a Vineland-II score or 85 to a difference of À19.18 [À12.28, À26.87] for a Vineland-II score of 40.

Objective: Niemann-Pick disease type C1 (NPC1) is a lysosomal storage disease characterized by progressive neurodegeneration, with the age of diagnosis ranging from the prenatal period through adulthood. Although neurological symptoms usually precede genetic diagnosis, they do not necessarily prompt diagnosis in the early years. Few prospective data are available to describe neurological onset, including neurodevelopmental delays, in children with NPC1. This dearth of information hinders the planning and implementation of adequate monitoring and treatment for the neurodevelopmental sequelae of NPC1. Method: Twenty-nine infants, toddlers, and preschoolers younger than 6 years participated in a natural history study and were administered neurodevelopmental assessments using instruments commonly used for early intervention screening in the community. Results: Twenty-two of 29 participants met the criteria for a significant delay of at least 1.5 SDs below the mean in at least one domain of development; the youngest children often met these criteria for a significant delay based on motor delays, but cognitive and language delays were also common. However, only 11 of the 22 participants were reported to receive early intervention services before study entry. Conclusion: Although neurological symptoms may not prompt the genetic diagnosis of NPC1, the current findings support the use of a multimethod approach to repeated assessments for young children with the diagnosis because of the frequency of developmental delays or decline in multiple domains. The diagnosis of NPC1 alone should qualify children for evaluation for early intervention services and consideration of investigational therapeutic interventions.

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