Background Autism spectrum disorder (asd) is a complex developmental condition and ‘gold standard’ diagnostic assessment for asd is a multi-dimensional process. in our clinic this includes a standardised developmental interview (3di), and direct interactive observation of the child using a standardised, semi-structured measure (ados-2). one complexity of diagnostic assessment is that around 70% of children with asd present with one or more co-morbidities, such as mental health difficulties and additional developmental disorders. approximately 40% of children with asd meet criteria for an anxiety disorder, one of which is selective mutism (sm; dsm-5), characterised by the inability to speak in specific circumstances. such children speak confidently in some situations while consistently failing to speak in others, where there is an expectation of speaking. a recent study reported that 69% of children with sm also had diagnosis of a developmental disorder, 7% were diagnosed with aspergers syndrome, a form of asd.

Methods In our specialist asd assessment clinic, we receive a growing number of referrals of children with sm, where asd is also suspected. assessing for social communication is key, but presents challenges when a child does not speak in clinic. currently there is limited research and no agreed assessment protocol for diagnosing asd in children with sm. using case studies, we are developing an assessment protocol for diagnosing asd in children presenting with sm. this includes extending initial assessment to understand the child’s sm presentation and impact. the information is then used to plan necessary modifications to the ados-2 and additional observations to ensure comprehensive assessment, despite the child’s lack of speech in clinic.

Conclusions We propose that sensitive, creative and carefully individualised approaches are necessary and possible when assessing asd in children with sm, while maintaining a standardised process to ensure the reliability and validity of the diagnosis.