Understanding Autism Diagnostic Tests: 8 Things You Should Know


In this blog, we cover the purpose and process of conducting a diagnostic evaluation for Autism Spectrum Disorder (ASD). You will learn what the evaluator is looking for, what areas are evaluated, what kinds of tests are used, and what to expect during and after the evaluation.

Over the past several years we have seen an increase in the number of children diagnosed with ASD. Current estimates published by the US Centers for Disease Control indicate that approximately 1 in 59 children are diagnosed with Autism Spectrum Disorder (roughly 1.7 percent of US children).

Understanding how a child is diagnosed with ASD is important for parents, educators, therapists, and anyone interested in increasing their knowledge on this subject.

What is the purpose of a diagnostic evaluation?

Because there are no lab or other medical tests that can diagnose ASD, we focus on behaviors that can be observed by parents, teachers, and others. To help us figure out if a child has ASD (often called being “on the spectrum”), we need to observe and evaluate his or her development in several key areas. These areas include language & communication, social awareness and interaction, and restricted interests & repetitive behaviors. The purpose of the diagnostic evaluation is to discover whether the child has any symptoms of ASD, how many symptoms they have, and how much those symptoms impact the individual’s ability to fully interact with their environment.

How are ASD symptoms evaluated?

The evaluation of ASD symptoms should include at least two key components: Parent/Caregiver Interview and Direct Observation. The parents/caregivers are interviewed about the child’s development from birth to the time of evaluation and will focus on symptoms of ASD specifically. This interview may also explore pregnancy and birth history, health history, school history, behavioral and emotional health, and any other details that may affect the child’s behavior or development. The child must also be observed by a trained evaluator who can determine if symptoms reported in the interview are visible to others.

In many cases parent/caregiver interview and direct observation are enough to evaluate the ASD symptoms. In some situations, it is helpful to interview the child’s teacher or other adults who know the child well. This can be done in person or over the phone.

The goal is to have enough information about the child to understand how she functions in different environments. The person conducting the evaluation compiles all of the information and applies his or her training and experience to determine the diagnosis.

What tests are used during a diagnostic evaluation?

Our ASD specialists are trained to use a test called the Autism Diagnostic Observation Schedule (ADOS, for short). The ADOS is a test that helps a trained evaluator make objective ratings of the child’s behavior and determine whether the behavior pattern suggests a diagnosis of ASD.* It takes between 30 and 60 minutes to conduct the ADOS test.

The ADOS is a sequence of play and social activities that are done with the child. In young children, the parent is also present, allowing for observation of the child’s interaction with familiar adults. The ADOS activities provide an opportunity to observe the child’s social and communication skills and any repetitive behaviors that happen frequently.

Other tests for autism might include the Social Communication Questionnaire, Autism Spectrum Rating Scales, Social Responsiveness Scale, Gilliam Autism Rating Scale, and others.

It is not required that a particular test be given in order to determine a diagnosis of ASD. There is no test that can make the diagnosis without the skilled clinical judgment of the evaluator. However, the ADOS is often a very helpful tool during the direct observation part of the evaluation. Some in the field of ASD consider it essential.

*Note – children in Utah who have Medicaid insurance are required to have the ADOS test in order qualify for autism treatment services.

What other areas are evaluated during a diagnostic evaluation?

Because ASD is a developmental disability, the evaluation will usually include tests of language, intelligence, behavior, and adaptive behavior (daily living skills and activities). Some tests are given directly to the child, and others are forms completed by the parent/caregiver. Depending on the child, other areas of evaluation may include attention, memory, motor functioning, and academic achievement. Evaluation of these areas is not always possible, or necessary, in order to diagnose autism. However, this additional evaluation can often help to better understand the child’s current levels of functioning and guide treatment and education decisions.

A skilled evaluator will always objectively consider other possible diagnostic explanations or conditions that may happen along with, or in place of, ASD. They seek to answer the question, “What explains the challenges this child is having, and that are a concern to his parents and teachers?” This leads to far greater understanding of the child than simply answering the question, “Does this child have ASD?”

Who can diagnose a child with ASD?

Autism Spectrum Disorder can be diagnosed by a medical or mental health professional with knowledge of ASD. There is a growing understanding of the importance of specialized training for professionals and also the use of high-quality diagnostic tools and methods. Some agencies may not regard a diagnosis of ASD as “official” unless it was made by a psychologist, developmental pediatrician, or neurologist. Some agencies may require the use of a specific test (often the ADOS) when deciding whether a child qualifies for services or benefits.

At ABS, our evaluators are psychologists with advanced training and experience in conducting diagnostic evaluations. We strive to always conduct a thorough evaluation of both the child’s disabilities and strengths and abilities.

How long does the diagnostic evaluation take?

At ABS, due to the comprehensive nature of our evaluation process, a typical evaluation generally lasts 3 hours for a young child (under 5) and up to 6 hours for an older child. This includes the parent/caregiver interview, direct observation, and giving various other tests.  Breaks are provided regularly to keep the child comfortable and maintain optimal energy and cooperation. The psychologist usually spends 2-4 hours after the evaluation to score and interpret all the tests and write up a report.

What happens after the diagnostic evaluation?

Parents/caregivers schedule and attend a feedback meeting after the testing visit in which the evaluator will review the results of the evaluation and explain the diagnosis, recommend appropriate treatments, and discuss ways to help the child at school. We will also discuss whether there are any other evaluations the child might need. Additional evaluations might include speech/language, occupational therapy, and ABA assessment.

The final step is to receive a report of the evaluation, summarizing the parent/caregiver interview, direct observation, results of all tests and forms, recommendations for treatment, and resources the family may use to obtain additional information, support, etc.

What can I expect from the diagnostic evaluation?

A comprehensive evaluation will result in an increased understanding of your child’s unique strengths and challenges, diagnosis and severity of the condition at the time of the evaluation, and direction regarding treatment and educational planning.