Aim We examined key features of two outcome measures for social dysfunction and autism spectrum disorder traits, the Social Responsiveness Scale, Second Edition (SRS‐2) and the Social Skills Improvement System – Rating Scales (SSIS‐RS), in children with neurofibromatosis type 1 (NF1). The aim of the study was to provide objective evidence as to which behavioural endpoint should be used in clinical trials. Method Cross‐sectional behavioural and demographic data were pooled from four paediatric NF1 tertiary referral centres in Australia and the United States (N=122; 65 males, 57 females; mean age [SD] 9y 2mo [3y], range 3–15y). Results Distributions of SRS‐2 and SSIS‐RS scores were unimodal and both yielded deficits, with a higher proportion of severely impaired scores on the SRS‐2 (16.4%) compared to the SSIS‐RS (8.2%). Pearson’s product‐moment correlations revealed that both questionnaires were highly related to each other (r=−0.72, p<0.001) and to measures of adaptive social functioning (both p<0.001). Both questionnaires were significantly related to attention‐deficit/hyperactivity disorder symptoms, but only very weakly associated with intelligence. Interpretation The SRS‐2 and SSIS‐RS capture social dysfunction associated with NF1, suggesting both may be suitable choices for assessing social outcomes in this population in a clinical trial. However, careful thought needs to be given to the nature of the intervention when selecting either as a primary endpoint. What this paper adds The Social Responsiveness Scale, Second Edition yielded a large deficit relative to population norms. The Social Skills Improvement System – Rating Scales yielded a moderate deficit relative to population norms. Both scales were highly correlated, suggesting that they are measuring a unitary construct.

ObjectiveRapid developments in understanding the molecular mechanisms underlying cognitive deficits in neurodevelopmental disorders have increased expectations for targeted, mechanism‐based treatments. However, translation from preclinical models to human clinical trials has proven challenging. Poor reproducibility of cognitive endpoints may provide one explanation for this finding. We examined the suitability of cognitive outcomes for clinical trials in children with neurofibromatosis type 1 (NF1) by examining test‐retest reliability of the measures and the application of data reduction techniques to improve reproducibility.MethodsData were analyzed from the STARS clinical trial (n = 146), a multi‐center double‐blind placebo‐controlled phase II trial of lovastatin, conducted by the NF Clinical Trials Consortium. Intra‐class correlation coefficients were generated between pre‐ and post‐performances (16‐week interval) on neuropsychological endpoints in the placebo group to determine test‐retest reliabilities. Confirmatory factor analysis was used to reduce data into cognitive domains and account for measurement error.ResultsTest‐retest reliabilities were highly variable, with most endpoints demonstrating unacceptably low reproducibility. Data reduction confirmed four distinct neuropsychological domains: executive functioning/attention, visuospatial ability, memory, and behavior. Test‐retest reliabilities of latent factors improved to acceptable levels for clinical trials. Applicability and utility of our model was demonstrated by homogeneous effect sizes in the reanalyzed efficacy data.InterpretationThese data demonstrate that single observed endpoints are not appropriate to determine efficacy, partly accounting for the poor test‐retest reliability of cognitive outcomes in clinical trials in neurodevelopmental disorders. Recommendations to improve reproducibility are outlined to guide future trial design.

Objective: We examined the contribution of attention and executive cognitive processes to ADHD symptomatology in NF1, as well as the relationships between cognition and ADHD symptoms with functional outcomes. Methods: The study sample consisted of 141 children and adolescents with NF1. Children were administered neuropsychological tests that assessed attention and executive function, from which latent cognitive variables were derived. ADHD symptomatology, adaptive skills, and quality of life (QoL) were assessed using parent-rated questionnaires. Path analyses were conducted to test relationships among cognitive functioning, ADHD symptomatology, and functional outcomes. Results: Significant deficits were observed on all outcome variables. Cognitive variables did not predict ADHD symptomatology. Neither did they predict functional outcomes. However, elevated ADHD symptomatology significantly predicted functional outcomes. Conclusion: Irrespective of cognitive deficits, elevated ADHD symptoms in children with NF1 negatively impact daily functioning and emphasize the importance of interventions aimed at minimizing ADHD symptoms in NF1.