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Autism Study Evaluation

Photo: A boy lying in the grass.About Autism Spectrum Disorders (ASDs)

Autism spectrum disorders (ASDs) are a group of developmental disabilities that can cause social, communication and behavioral challenges. ASDs are “spectrum disorders.” That means ASDs affect each person in different ways, and can range from mild to severe. People with ASDs share some similar symptoms, such as problems with social interaction. But there are differences in when the symptoms start, how severe they are, and the exact nature of these symptoms. Determining the number of children with ASDs can be challenging due to the difference in symptoms and because there is no medical test, like a blood test, to diagnose the disorders.

Determining How Many People Have ASDs

The Centers for Disease Control and Prevention (CDC) developed a population-based tracking system to estimate the number of children with ASDs (prevalence) and collect information on features of these children. This tracking system finds children with ASDs by reviewing health and education records.

Learn more about the ASD prevalence from this system »

Evaluating CDC’s Tracking System

For the first time, CDC evaluated the tracking system that is used to estimate the prevalence of ASDs. Validation studies that evaluate tracking systems, such as this one, allow CDC to make informed changes in order to provide the most complete prevalence estimates.

Important findings from the study include:

  • The CDC tracking system is likely not over-estimating the prevalence of ASDs.
    • Most children found to have an ASD by a clinical examination were also detected by the tracking system.
  • The CDC tracking system missed 12 of 177 children who were examined and found to have an ASD. This result shows we are likely not counting some children with ASD.
Records-Based Approaches to Tracking ASD Prevalence

One way to track prevalence is by using a records-based approach. Records-based methods are a helpful way to track disorders that can be hard to diagnose, such as ASDs. A records-based approach allows CDC to count children with behaviors like those of a child with ASD but who may not have a formal diagnosis. This approach also allows CDC to collect information on ASD symptoms and features over time.

Next Steps

The results of the recent evaluation study are not directly comparable to other studies because it is the first population-based, records-review validation study for ASDs. However, this study showed that our records- based tracking system is a valuable tool for estimating ASD prevalence. This tool is more feasible than examining every child in a given population and it also may be more thorough than other methods which rely on an ASD diagnosis alone.

CDC has identified ways to improve the tracking system in order to provide the most complete prevalence estimates. Some of these improvements have already been made. For example, some children diagnosed with an ASD by a health professional did not have health or education records available for review. Therefore, CDC has strengthened efforts to locate hard-to-find records.

More Information


Avchen, R., Wiggins, L.D., Devine, O. , Van Naarden-Braun, K., Rice, C., Hobson, N., Schendel, D., & Yeargin-Allsopp, M. (2010). Evaluation of a Records-Review Surveillance System Used to Determine the Prevalence of Autism Spectrum Disorders. Journal of Autism and Developmental Disorders. Advanced On-line Publication.

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