Direct in-Person Assessments Add Value When Discerning Autism Spectrum Disorder in SMC1A Variants.

Background:

The neurodevelopmental phenotype in individuals with SMC1A variants includes intellectual disability (ID), autism spectrum disorder (ASD) and self-injurious behavior (SIB). A reciprocal interaction exists between neurodevelopmental characteristics, physical phenotype and environment. Differentiating ASD from (profound to severe) ID can be difficult. Individuals with a (severe) ID may meet diagnostic criteria for ASD based on proxy-administered questionnaires, while clinical assessment of their daily functioning may not confirm ASD. This discrepancy can often be explained by the abilities matching their developmental age, which questionnaires do not take into account.

Objectives:

To explore the added value of direct in-person assessments in individuals with SMC1A variants in order to discern ASD from ID and improve our understanding of the neurodevelopmental phenotype.

Methods:

We collected data from behavioral questionnaires in 31 participants (21 international and 11 Dutch) with a SMC1A variant. After informed consent from parents, three authors (PAM, AL, SP) performed interviews and direct in-person neurodevelopmental assessments in a Dutch sample of eight participants. Assessment battery included Autism Diagnostic Observation Schedule - 2 (ADOS-2), Autism Questionnaire (AQ), Bayley III, Wechsler Intelligence Scale (WPPSI-III and WAIS-IV)), Vineland-2, and Short Sensory Profile (SSP)).

Results:

Based on the Social Communication Questionnaire (SCQ) 18/24 participants scored within the clinical cut-off for ASD. For the Dutch group, all eight scored within the clinical range for ASD on the SCQ. Four out of eight participants met ASD criteria based on assessment with the ADOS-2. After careful analysis, two authors (PAM, AAL) agreed that only two of these four participants were impaired by ASD in daily functioning when considering their developmental level (profound and moderate ID). Three of eight participants had a profound ID, 1/8 severe, 1/8 moderate and 2/8 mild and 1/8 scored borderline to normal functioning. Deficits in adaptive abilities were not in line with cognitive abilities (e.g. communication skills were poorer than expected based on developmental level).

Severe difficulties in sensory information processing were present in most participants, more processing time was needed, and shifting between tasks was delayed. Repetitive and restricted behavioural patterns were common.

Conclusions:

From these direct assessments, a clearer picture of neurodevelopmental functioning of individuals with SMC1A variants has emerged. Autism may be assumed in a larger population based on questionnaires, but is less frequently diagnosed after direct in-person assessment and considering behavior in light of developmental level. Direct in-person assessment provides valuable and specific information relevant to understanding the neurodevelopmental phenotype in individuals with SMC1A variants.