Stability and Change for Toddlers with Autism Spectrum Disorder before Age 2: A 1.5-Year Follow-up

Background: Autism spectrum disorder (ASD) is thought as an innate neurodevelopmental disorder and characterized by impaired social communication and social interaction, as well as restricted and repetitive patterns of behavior and interest. Once thought to be a rare condition, ASD has recently emerged dramatically. The prevalence of ASD increases significantly beyond than 1 in 100 children (APA, 2013; Baird et al., 2006; Centers for Disease Control and Prevention, 2014). The increasing prevalence rate is due to improved awareness of ASD and service availability, and also highlights the importance of the early identification. Knowing the importance of early identification, the American Academy of Pediatrics (AAP) has recommended that all toddlers should receive screening for autism before age 2 (Johnson et al., 2007). 

Objectives:  A diagnosis of children with ASD appears to be stable in children as young as age 3. However, few studies examined stability and change of diagnosis for young children with ASD, especially for toddler before age 2. In this current study, longitudinal design was used to examine stability and change of diagnosis for toddlers with ASD before age 2.

Methods:  There were 98 participants who had all administrated both of the Screening Tools for Autism in Two-Year-Olds, Taiwan version (T-STAT) (Chiang et al., 2013) and Autism Diagnostic Observation Schedule (ADOS) (Lord et al., 1999) between 17 and 24 months of age (Time 1, mean chronological age = 21 months) and received diagnostic and developmental reassessment between 35 and 46 months of age (Time 2, mean chronological age = 40 months). At Time 2, all participants were assessed and diagnosed according to DSM and with reference to developmental history and current concerns from parents, results of cognitive and adaptive function measures, observations of the child, and the results of ADOS by a multidisciplinary team that included senior child clinical psychologists with Ph.D. degree and senior child psychiatrists.

Results:  Based on classification of the T-STAT (cutoff = 2.25), the results showed that the sensitivity and specificity are .89 and .81, respectively. In addition, positive predictive value (PPV) is .88 and negative predictive value (NPV) is .92. However, based on classification of the T-STAT (cutoff = 2.50), the results showed that the sensitivity and specificity are .87 and .83, respectively. In addition, PPV is .82 and NPV is .88. Based on classification of the ADOS (Time 1), the results showed that the sensitivity and specificity are .91 and .90, respectively. In addition, PPV is .89 and NPV is .92.

Conclusions: The results of this current study showed that reliable diagnosis of toddlers with ASD could be made before age 2 and have good short-term stability. In addition, the results of the current study showed that both the T-STAT and ADOS are promising tools to differentiate toddlers with ASD and toddlers with developmental delayed before age 2.