Results suggest that face-to-face administration of the TAND Checklist led to increased clarity, providing good support for the face-to-face approach when using the TAND Checklist. Examination GSI-IX mw of internal consistency suggested that the TAND Checklist has acceptable to excellent internal consistency within the domains and subdomains measured. The items from the psycho-social domain did not appear to have good internal consistency. On closer inspection, the three elements of this item include intra- and interpersonal

factors (self-esteem, family stress and parental relationship stress), where high internal consistency may not be expected. We suggest that the psycho-social domain should therefore be used simply as an introduction

to a conversation about this important level of investigation. One of the main objectives of the study was to investigate external validity of the TAND Checklist domain and subdomains. The behavioural domain items of the TAND Checklist correlated very strongly with the total difficulties score of the SDQ, suggesting that the TAND Behaviour Question may be helpful at identifying a range of behavioural difficulties that may underlie a range of psychopathologies as screened for using the SDQ. Results within the subdomain of hyperactivity also showed strong correlation between items associated with hyperactivity in the TAND Checklist and GSK126 the total hyperactivity/inattention score produced by the SDQ assessment tool, suggesting that endorsement of the hyperactivity items on the TAND Checklist should raise the clinical suspicion of ADHD or an attention-related disorder. The TAND Checklist social communication subdomain constructs

over correlated strongly with items from the SCQ, highlighting behaviours associated with autism spectrum disorders. Findings suggested that these items may be very useful markers of risk for ASD which is known to have a very high prevalence in TSC. Overall, results from the behavioural domain suggested that ADHD-related and ASD-related behaviours, two key developmental challenges in TSC, may usefully be identified through the TAND Checklist. There was a moderate correlation between the level of intellectual ability as perceived by parents and researcher judgement based on the Wessex scale. Results suggest that parental perception of intellectual development is generally reasonably accurate. Given the multi-componential nature of intelligence, all individuals with TSC are recommended to have a formal assessment of their intellectual strengths and weaknesses at key developmental timepoints.9 At the neuropsychological level, the TAND Checklist showed very strong correlation with the BRIEF.