ADDM Network Methods
The Autism and Developmental Disabilities Monitoring (ADDM) Network is the only collaborative network to track the number and characteristics of children with ASD in multiple communities in the United States. Since the launch of the ADDM Network in 2000, CDC has funded 17 sites in areas of Alabama, Arizona, Arkansas, California, Colorado, Florida, Maryland, Minnesota, Missouri, New Jersey, North Carolina, Pennsylvania, South Carolina, Tennessee, Utah, West Virginia, and Wisconsin. CDC also operates an additional ADDM site in Georgia. The ADDM Network tracks more than 220,000 8-year-old children and 220,000 4-year-old children. The ADDM Network is following-up on a cohort of 16-year-old children in select states.
The ADDM Network’s goals are to
- Obtain as complete a count as possible of the number of 8-year-old and 4-year-old children with ASD in each ADDM Network area and identify changes in that count over time;
- Provide information about early identification of children with ASD, including ages of evaluation and diagnosis;
- Describe health and service needs of adolescents with ASD;
- Provide information on the characteristics of children with ASD, including sex, race/ethnicity, co-occurring intellectual ability;
- Determine whether ASD is more common in some groups of children (for example, among boys versus girls) than among others, and if those differences are changing over time; and
- Understand the impact of ASD and related conditions upon children, families, and communities in the United States.
How does ADDM develop estimates?
The ADDM Network estimates the number of children with ASD using a record review method to find children who have received an ASD diagnosis, an autism special educational classification, or an ASD International Classification of Diseases (ICD) code from a community health or education service provider. Additional information is collected from records to provide information about demographic characteristics and other important health conditions, like co-occurring intellectual disability.
What are the different ways of estimating the number of children with ASD?
There are several different ways to estimate the number of children with ASD, and each method has its advantages and disadvantages.
|Method||What Is It?||Advantages and Disadvantages|
|Population-based screening and evaluation||Screening and evaluating a sample of all children in a population, within a defined age group.||Can provide high accuracy, but can be costly and time-consuming, and might produce skewed results based on who agrees to participate.|
|National surveys||Collecting information via standardized instruments, such as telephone interviews or self-completed questionnaires.||Is representative of national characteristics, but might reflect bias based on who participates and how ASD is defined and reported.|
|Registries||Collecting information on children and families who voluntarily include themselves on a list of people affected by ASD.||Relatively low cost, but time-consuming and includes only individuals with a clear diagnosis and families who know about the registry and are willing to be on the list.|
|Administrative data||Looking at codes for services in records from Medicaid and agencies, such as the U.S. Department of Education.||Relatively low cost, but can underestimate prevalence because not all children with ASD are receiving services for ASD or have been diagnosed with ASD.|
|Systematic record review (ADDM Network’s Method)||Linking and reviewing health, service, and special education records to identify and describe characteristics of children with ASD.||Relatively low cost, but challenging to link children across multiple data sources, as all children with ASD may not be identified by a single provider or data source.|
What are the advantages of the ADDM Network method?
There are several major advantages to using the ADDM Network method for tracking the number and characteristics of children with ASD. For example, the ADDM Network
- Is the largest, ongoing ASD tracking system in the United States;
- Uses a method that is population-based, which means we try to identify all the children with ASD from the entire population of children in a defined geographic area (or multiple geographic areas);
- Can track changes over time within different communities and within different groups (such as racial/ethnic groups); and
- Collects and links information from multiple sources in the community where children are served, including schools, local clinics, and service providers.
For the younger population, the ADDM Network tracks children who are at high risk for ASD based on a community provider’s suspicion that ASD is present.
What else is the ADDM Network doing?
To better understand early ASD identification, in 2018 the ADDM network expanded from tracking 4-year-old children in portions of 6 sites to all 11 sites (Arkansas, Arizona, California, Georgia, Maryland, Minnesota, Missouri, New Jersey, Tennessee, Utah, and Wisconsin). Sites tracked 4 year old children who either had a diagnosis or special education eligibility of ASD or who were suspected of having ASD by a community provider.
Also, in 2018, 5 ADDM Network sites (Arkansas, Georgia, Maryland, Utah, and Wisconsin) followed up on children who were 16 years of age in 2018 whose records were previously reviewed by ADDM sites in 2010 when they were age 8. These data allow comparison of child characteristics between children identified with ASD by the age of 8 versus age 16. In addition, the data provide information about co-occurring health conditions and educational transition planning among children identified with ASD at age 16 years.