Diagnostic Stability and Outcome of Toddlers with Significant Cognitive Delays and ASD Symptoms

Background: As awareness of the importance of early detection of autism spectrum disorders (ASDs) has grown, diagnoses have been occurring younger and in children with more severe cognitive delays.  However, it is not clear whether diagnoses made in young, significantly delayed children are stable and what their prognoses may be. In our Early Detection study, we do not diagnose a child with an ASD if all mental age equivalents are under 12 months, but put them in a separate category, "ASD-low MA," since the diagnostic stability is unknown.

Objectives: To examine the diagnostic stability, prognosis, and characteristics of a cohort of children with significant developmental delays who were diagnosed with "ASD-low MA" at a young age.

Methods: Children received comprehensive evaluations at approximately ages 2 and 4 after screening positive on the M-CHAT.  Twelve children (7% of the total sample of children with ASDs seen at both time points) had developmental levels below 12 months, as well as significant symptoms of an ASD, at initial evaluation.  Autistic symptoms at both evaluations, as well as diagnosis at re-evaluation, were analyzed in this sample of children.

Results: The children, who were evaluated initially at a mean age of 25 months (SD=4.8, range=18.6-31.8), had mean nonverbal age equivalences of 8 months, as well as receptive and expressive language skills estimated at the 10 and 9 month level, respectively.  Their mean CARS score was 35.6 and total scores on Module One of the ADOS (social plus communication) ranged from 11 to 21 (mean=17.7).  They averaged 6.8 DSM-IV-TR symptoms of autism (range=3-9) and 10 of the 12 children displayed repetitive or stereotyped behaviors, which are typically less frequent in this age group.  At re-evaluation (mean age=50 months; SD=4.8; range=41.8-57.7), all children continued to meet ASD criteria; 11 were diagnosed with Autistic Disorder and one remained classified as “ASD-low MA.”  Their mean nonverbal level was 20.3 months (SD=6.6, range= 11-33), with receptive language estimated at 16.1 months (SD=7.1; range=5-26) and expressive language at 15.7 months (SD=8.1; range=6-27); standard scores were all at floor level.  The children's Vineland standard scores were all below 75, with the mean scores on all domains below 60.  They continued to display significant symptoms of ASDs at re-evaluation; mean CARS score were 35.0, mean total ADOS (Module One) scores were 15, and the mean number of DSM-IV-TR symptoms was 6.7.  At re-evaluation, all children displayed repetitive or stereotyped behaviors, most frequently stereotyped motor mannerisms (82% of the cohort).

Conclusions: Diagnostic and symptom stability was strikingly strong in this sample of young children presenting with severe developmental delays and symptoms of ASDs.  All of the children met DSM-IV-TR criteria for Autistic Disorder as well as mental retardation when re-evaluated.  It is notable that the majority of children displayed stereotyped behaviors from an early age and that all presented with them at re-evaluation.  This study suggests that diagnoses of ASDs can be made reliably in young children with ASDs and significant developmental delays, with the prognosis poor in this subsample of children.