Objectives: To examine the stability of a diagnosis of ASD made in children by age 24 months (mo) and to explore characteristics at presentation and interventions associated with best outcomes.
Methods: Retrospective chart review of 44 children presenting by age 24 mo to a University Affiliated Early Intervention program from 2003 to 2008 who received an ASD diagnosis based on multidisciplinary evaluation and who had follow-up at least 1 year later. Data from initial evaluation included: age, demographics, cognition, autistic features based on the DSM-IV criteria, Childhood Autism Rating Scale (CARS) and, in some, the Autism Diagnostic Observation Schedule (ADOS). ASD diagnosis at follow-up was based on CARS (76%), DSM-IV (29%), ADOS (16%), and Board of Education classification/autism-specific class placement (93%). Type/hours of intervention received by each child per week (applied behavioral analysis, speech, occupational and physical therapies, family training) were tabulated. Data of those who retained ASD diagnosis and those who did not were compared. For children with multiple follow-up visits, the most recent data was utilized for follow-up analysis. Statistical analysis included chi-square, t-test and nonparametric testing.
Results: Mean age of the sample was 19.7 ± 2.8 mo (12-24 mo); 63% were male; 20% had cognitive standard score ≥70. Fourteen (32%) were diagnosed with autism and 30 (68%) with ASD; At follow-up, mean age was 51 ± 18 mo (29-117 mo). ASD diagnostic classification of the sample at follow-up was as follows:
ASD Diagnostic Classification at Follow-up
|Diagnosis at Follow-up|
|Diagnosis at Presentation||Autism||ASD||No ASD|
|Autism (N=14)||12 (86%)||2 (14%)||0|
|ASD (N=30)||7 (23%)||15 (50%)||8 (27%)|
Children who no longer met criteria for ASD were more likely initially to have lower CARS score (32.2± 2 vs. 35.5± 5, p=0.006), higher cognition (Standard Score: 62± 1.2 vs 50.3± 3, p=0.005), and evidence of conversational ability on the DSM-IV (29% vs 0%, p=0.03) suggestive of more language.There were no differences in age at initial evaluation, length of time between original diagnosis and follow-up, and type/hours of intervention between those who retained an ASD diagnosis and those who did not.
Conclusions: In this sample, the diagnosis of ASD made in children under 2 years of age was quite stable. A diagnosis of autism was more stable than ASD. The likelihood of moving off the autism spectrum was increased for those children with milder autistic symptomatology, higher cognition, and more language at presentation.