Social skills and autism spectrum disorder symptoms in children with neurofibromatosis type 1: evidence for clinical trial outcomes

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.