Clinical Characteristics of Children Diagnosed with Autism Spectrum Disorder as Toddlers (<3 yr) vs. as Preschoolers (3-5 yr)

Background:

There is a thrust for earlier identification of children with ASD so that timely intensive therapeutic programs can be initiated.  Limited information exists about the clinical profile of children receiving an early diagnosis, with discrepancy in the literature regarding whether children identified earlier have more severe impairment.

Objectives:

To compare the clinical presentation of children diagnosed with ASD before age 3 to children diagnosed after age 3 in a community sample.

Methods:

Retrospective chart review of 323 children, ages 1 to 6, presenting to a University Affiliated Program for multidisciplinary evaluation from 2003 to 2008, who received a diagnosis of ASD.  Information reviewed included demographics, medical, developmental, and family histories, DSM-IV symptom checklist, Childhood Autism Rating Scale (CARS), and cognitive level.  Statistical analysis included Chi-Square, T-test, Mann-Whitney test, and logistic regression.

Results:

Of the 323, 155 were under 36 months (range 18-72 mo.).  Children diagnosed under 3 were more likely to present toe walking (39% vs. 22%, p = 0.001) and language regression (22% vs. 13%, p = 0.04).  There were no significant differences in maternal age or family history of autism.  There were no significant differences in autistic symptom severity as assessed by the total CARS score or in cognitive functioning (35% vs. 37% with IQ>70).  There were differences in the autistic symptom profile between the 2 groups.  On the DSM-IV, children under 3 were more likely to demonstrate lack of showing (61% vs. 33%, p<0.001), delay in spoken language (90% vs. 59%, p<0.001), and lack of social imitative play (70% vs. 50%, p = 0.003).  Preschoolers were more likely to present stereotyped language (76% vs. 36%, p<0.001), impairment in conversation (48% vs. 13%, p<0.001) and failure to develop peer relationships (78% vs. 57%, p = 0.001). These differences persisted after adjusting for maternal education, socioeconomic status, and cognitive level.

Conclusions:

Children diagnosed with ASD as toddlers are not more impaired in terms of autistic symptom severity or cognitive impairment when compared to children diagnosed as preschoolers.  The children diagnosed earlier are, however, more likely to display toe-walking, and to have a history of regression.  Different patterns of autistic symptomatology are also seen in the 2 groups.