Award Date


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Educational & Clinical Studies

First Committee Member

Nancy Sileo

Second Committee Member

Catherine Lyons

Third Committee Member

Richard Tandy

Fourth Committee Member

Amanda Higgins

Number of Pages



Early intervention for children with autism spectrum disorders (ASD) has significant impact on children and families. Early intervention optimizes long-term diagnosis for children with ASD. Unfortunately, many children with ASD are not diagnosed until after age three and often receive services from a local school district rather than through early intervention services. However, many of the symptoms of ASD can be hard to identify because symptoms during infancy may be more difficult to detect or may present differently than manifestations of the symptoms at older ages. Despite the difficulty in identifying symptoms of ASD in young children, there are certain indicators children under the age of three display that are consistent with ASD. Some symptoms may even be observable around 12 months of age.

In the last decade several promising screening instruments including the M-CHAT and PDDST-II have been developed and validated to aid in the diagnosis of ASD for children under two years of age. Nevertheless, a great deal of research still needs to be conducted on these tools. Most of the current research on these tools has focused on the original development of the tools. Longitudinal studies are needed to examine whether the original samples that were used to validate these tools would still meet the diagnostic criteria for ASD. In addition, cross validation of these tools should be conducted using new samples of children. Finally, research is needed to compare the tools to determine which tool is a better predictor of ASD in young children.

This study compared the accuracy of the results of M-CHAT and PDDST-II Stage One and Stage two screeners with the results of the Autism Diagnostic Observation Scale (ADOS) for a group of children under the age of three (N=80). Eighty children were screened with two screeners (MCHAT and PDDST-II Stage One) during the eligibility appointment at local early intervention agencies or during the mandated 18 or 24 month screening for ASD. These 80 children were then re-screened using the PDDST-II Stage Two and evaluated using the ADOS at a follow-up appointment. The results of all three screeners were compared with the results of the ADOS to determine the level of sensitivity and specificity for all three screeners. The PDDST-II Stage One results were compared with the PDDST-II Stage Two results to determine whether using a Stage Two screener decreases the number of false positives, therefore, reducing the number of children that require further diagnostic testing. The results of this study indicate that the PDDST-II Stage Two was the best predictor of ASD in children who were enrolled in early intervention programs. The PDDST-II Stage Two resulted in highest levels of sensitivity and specificity. In addition, the PDDST-II Stage Two reduced the number of children requiring further assessment that were identified as being at risk for ASD by the MCHAT and the PDDST-II Stage One. Further research should be completed in order to replicate the results of this study in order to validate the use of the PDDST-II Stage Two as screener with the early intervention population.


Assessment; Autism; Autism spectrum disorders – Diagnosis; Autism spectrum disorders in children; MCHAT; PDDST-II; Screening Instruments


Pediatrics | Special Education and Teaching

File Format


Degree Grantor

University of Nevada, Las Vegas




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