Centers for Disease Control and Prevention. (2020, March 13). Screening and diagnosis of autism spectrum disorder. Centers for Disease Control and Prevention. https://www.cdc.gov/ncbddd/autism/screening.html. 

Screening and Diagnosis for ASD: CDC

Matching procedures in autism research: Evidence from meta-analytic studies

Grinnell College

There is no medical test for ASD. Rather, experts must study an individual's development and behavior and, using their best logic and existing criteria, suggest a diagnosis. Generally, diagnoses are more likely to be accurate by age 2 or older. 

ASD Diagnosis Techniques

Diagnosis technique library

In order to diagnose or understand ASD, there need to be comparisons to other groups of people and the peers of the child with autism. There might be a difference in the mental age of the child compared to their chronological age, which can only be seen through comparisons. Does the child have a delay in reaching developmental milestones that their peers reached? Are their developmental milestones more in line with that of a different chronological age group, or do they have altered responses in behavior than expected to people of the same mental age?

A child with autism might be able to explain and understand where emotions come from without being able to reflect or understand the emotions themselves. This is an altered response.

ASD Diagnostic Comparisons

Prior to DSM-5, there were multiple separate diagnoses under the broad range of the Autism Spectrum, but now they are simply denoted as ASD. The single diagnosis of ASD replaced the subcategories that existed prior. To be diagnosed, the individual must have persistent difficulties in social skills and communication and restricted and repetitive behaviors that have been around since childhood. 
Screening is recommended at 18 and 24 months old during regular clinician visits, though more screenings could be recommended if the child is at higher risk. 

- Diagnostic Screening Tools
- Diagnoses Prior to DSM-5


Diagnosing ASD in Children (DSM-5)

Although autism spectrum disorder is typically diagnosed in children, research shows that more subtle presentations of ASD are often not identified until adulthood. Adult diagnosis is particularly common in autistic women, who are less likely to display stereotypical autistic traits and are more likely to internalize their presentation. Diagnosing autism in adults requires some modification of the typical approach used to diagnose children, including the use of different screening tools. As with child diagnosis, parental input is frequently sought for the diagnosis, but significantly more weight is placed on the individual’s self-report in adult diagnosis. 

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