Autism spectrum disorder (ASD) is a lifelong condition that’s often diagnosed in childhood. The process of arriving at that diagnosis, however, can be a confusing and sometimes convoluted ordeal. Because ASD is a heterogeneous condition, which can present very differently from patient to patient, autism testing isn’t a fully standardized process. Here’s what you need to know about autism testing and the myriad of diagnostic tools that may be involved.

What are the first steps in autism testing?

While the specific diagnostic tools used in autism testing can vary from case to case, there are two steps that are considered standard in diagnosing someone with autism:

• Developmental Screening

• Comprehensive Diagnostic Evaluation

What is developmental screening for autism testing?

Developmental screening—a short test that measures if a child is learning basic skills in the appropriate timeframe—is considered the first step in any autism diagnosis. Developmental screenings can be performed by a child’s pediatrician during regular visits and are typically done at least three times, at 9 months, 18 months, and finally at 24 or 30 months, with specific screenings for ASD typically happening at 18 and 24 months. Children who are at a high risk of developmental issues or ASD may require additional screenings. If a doctor notices any signs of autism or developmental problems, a comprehensive diagnostic evaluation will be performed.

What is a comprehensive diagnostic evaluation in autism testing?

Comprehensive diagnostic evaluation is the second step in diagnosing ASD. This is the stage where autism testing starts to become varied. The evaluation may include a review of the child’s behavior and development, hearing and vision screenings, genetic testing, and neurological testing, among other tests.

What diagnostic tools are used in autism testing? Many different diagnostic tools can be used in autism testing. Some of the most commonly-used assessments include:

• Autism Diagnosis Interview – Revised (ADI-R) The ADI-R is used to assess autism in both children and adults with mental ages of 18 months and above. The test is a 93-item questionnaire, which typically takes several hours to complete and focuses on three types of behavior: reciprocal social interaction; communication and language; and restricted and repetitive, stereotyped interests and behaviors.

• Autism Diagnostic Observation Schedule (ADOS) In ADOS testing, clinicians observe children’s social behavior, as well as their communication and imaginative skills. ADOS testing consists of four 30-minute modules and is highly customizable, as each is designed for the individual being tested and caters to their level of expressive language.

• The Modified Checklist for Autism in Toddlers (M-CHAT) The advantage of the M-CHAT is that it’s very quick and easy to administer. While the checklist isn’t always accurate, it is used to screen patients and determine a risk of ASD in the United States, the U.K. and several other countries.

• Childhood Autism Rating Scale (CARS) This assessment, which includes items drawn from several systems for diagnosing autism, can be used with any child who is at least two years old. These days, the CARS-2, an updated version of the test, is preferred. The original version of the scale was criticized for its shortcomings in diagnosing higher-functioning individuals with ASD. Under CARS-2, there are two forms, one for younger and/or lower-functioning patients and another for higher-functioning individuals. Like ADOS, CARS is designed to involve direct observation from a qualified clinician.

• Gilliam Autism Rating Scale – Second Edition (GARS-2) The GARS-2 can be used by teachers, parents, and clinicians to identify and diagnose people aged 2-22 on the autism spectrum, as well as identifying the severity of the condition.

Is there a genetic test for autism? Genetics play a huge role in autism—in fact, there are more than a 100 gene mutations known to be tied to condition. There are at least four types of tests that can detect these mutations, but there is no genetic test to detect or diagnose autism at this time, since not everyone with the gene mutations linked to autism ultimately develops ASD. As an example, while missing a stretch of chromosome 16 called 16p11.2 is linked to autism, only about one in four people who are missing 16p11.2 are actually on the spectrum.

In the end, autism testing is, by necessity, as varied as ASD itself and the tools used to diagnose autism must be tailored to the individual being tested.