The diagnostic behavioural assessment for autism spectrum disorders (DiBAS): A screening instrument for adults with intellectual disability suspected of autism spectrum disorders

Background: One in four individuals with intellectual disability (ID) are additionally diagnosed with autism spectrum disorders (ASD) that may not be recognized und thus remain untreated until adulthood. Diagnosing ASD in adults with ID is challenging and there is a lack of specific diagnostic measures. Methods: The Diagnostic Behavioral Assessment for ASD (DiBAS) is a DSM-5/ICD-10 based caregiver-report screener consisting of 20 Likert-scaled items. This study evaluates the item validities and -difficulties, and the scale's feasibility and validity in a clinical, adult ID sample (N=91) from 8/2009 to 12/2011. Results: The DiBAS was applicable in all individuals (100-%) and yielded an adequate diagnostic validity reflected by ROC analysis and an AUC of 0.808.-Using a cut-point of 30, the sensitivity and specificity values were 83-% and 64-%, the agreement with the final diagnostic classification was 74-%, and Cohen's kappa was 0.469.-Single item analysis revealed 12 valid DiBAS variables that predominantly could be assigned to the social interaction and non-verbal communication domains; item difficulties varied from 0.21 to 0.84.-The scale's internal consistency was appropriate (Cronbach's alpha 0.749). Conclusions: The DiBAS is a promising psychometrical sound scale of high feasibility to screen for ASD in adults with ID, which could be further specified by single item analysis