Autism Spectrum Tests for Children and Adults: A Nurse Practitioner Explains

The prevalence of autism spectrum disorder (ASD) has steadily risen over the years. According to the Centers for Disease Control and Prevention’s (CDC) in 2023, approximately 1 in 36 children receive an ASD diagnosis by the age of 8, which is an increase from 1 in 44 children in 2018.1

Early detection of ASD allows individuals to have timely access to intervention services that could give them an optimal quality of life. For example, health care professionals, particularly, pediatricians and primary care providers, can identify developmental delays and signs of ASD in children before they enter school through autism spectrum tests.2 This puts clinicians in a position to provide comprehensive support and resources tailored to patients unique needs at an early age.

ASD Screening Protocol

Experienced professionals can reliably and accurately diagnose ASD in children aged 18 months and younger.2-4 Children diagnosed with ASD at 18 months demonstrate less advanced language and adaptive skills than children who are diagnosed with ASD at 24 months or 3 years. Children diagnosed later often exhibit more advanced language skills and milder symptoms of ASD, necessitating ongoing surveillance during childhood.3

The American Academy of Pediatrics (AAP) guidelines for the identification, evaluation, and management of children with ASD recommend that every child undergo specific screening for ASD at regular well-child visits using the most valid and current measures at age 18 and 24 months.2,4 Clinicians must pay particular attention to children at higher risk for developmental delays, including those with parents or siblings who have ASD, those born preterm, and those with low birth weight.2

Diagnosing ASD

To get better insight into the process of evaluating and diagnosing ASD at different ages, including the use of autism spectrum tests, we spoke with Allison Paugh, a psychiatric mental health nurse practitioner (PMHNP) in Goldsboro North Carolina, who assesses, diagnoses, and treats a variety of mental disorders, including ASD, across the lifespan.

What is your process for diagnosing ASD as a nurse practitioner?

Paugh: Typically, the process of diagnosing autism involves pediatricians watching for any signs of abnormal developmental delays at every well-child visit at 6, 9, 12, 18, 24, and 30 months. In the case where the child hasn’t gone to pediatrics and the family comes directly to me, I do face-to-face observations and ask the parent detailed questions.

What validated autism spectrum tests do you use to screen for autism?

Paugh: I use the Autism Diagnostic Observation Schedule, Second Edition (ADOS®-2), which is the gold standard diagnostic test for autism used across the lifespan. Sometimes, I am able to know right away without any doubt that an individual has autism using this screening method, particularly if they are non-verbal. If this is the case, I don’t recommend any further psychological testing.

After using this screening method, if I suspect that it is more than likely autism, I almost always refer the child to one of the psychologists in my clinic to receive a deeper level psychologic and neurodevelopmental workup. My sessions are not very long, so I can’t do the battery of tests that psychologists do, which may take up to 3 or 4 hours to administer.

How do autism spectrum tests differ for a child vs an adult?

Paugh: ADOS can still be used for adults since it is used across the lifespan. There are several different screening tools used to diagnose autism for varying age groups, but there really isn’t 1 specific test just for adults.

I have noticed a trend of young adults coming to my office and wanting a formal evaluation to confirm the diagnosis of autism. Dr. TikTok and Dr. Google have potentially influenced this trend. In one way, it is so great to have this increased awareness and desire to do therapy when symptoms are recognized. It is much better to receive treatment at 15 than at 48.

When children are involved, parents fill out the screening questionnaires. Children also tend to have more providers involved in their diagnosis and treatment, including speech therapists and pediatricians, whereas adults don’t have as many disciplines involved in the process. Communication between providers from different disciplines is required, especially when children are being evaluated for ASD. Assessments with each provider take place on an individual basis instead of a setting where a group of providers observes the child.

Diagnosis of ASD often can be harder in adults because the provider needs a lot of background information about symptoms from childhood, which helps to substantiate that diagnosis. Obtaining a detailed childhood history may require adults to bring family members with them to the test.

There are several different screening tools used to diagnose autism for varying age groups, but there really isn’t 1 specific test just for adults.

Getting a reliable medical history may get increasingly difficult depending on the age of the adult being evaluated. Family members may have passed away, or it may be harder for family members or the adults themselves to remember events that occurred during childhood. Also, adults may not necessarily perceive their childhood memories to be abnormal.

Does age alter how autism manifests?

Paugh: Autism isn’t a progressive disorder, so it doesn’t worsen as people age. ASD usually is very apparent in children who are non-verbal, whereas adults seeking a diagnosis have milder symptoms that go unnoticed during childhood.

Signs or symptoms of ASD may become more apparent in adults when they live with their parents until their 20s or 30s. When the time comes where adults with ASD need to transition to independent living, they need to demonstrate specific life skills and face all of these new challenges on their own, so difficulties with this transition period may motivate them to seek a diagnosis.

Where do individuals get tested for ASD?

Paugh: I work in a private practice where we have 2 psychologists and other health care providers, such as myself, who can screen for and diagnose autism. The accessibility in 1 location for these families makes it a lot easier for interdisciplinary referrals to get second opinions and verification.

There are centers specifically designated for autism testing; however, the waitlist for these sites is incredibly long — sometimes even up to a year. Often, families will get the child’s name on a waitlist and then begin to look for a psychologist who specifically diagnoses autism. It can be very difficult to find a psychologist with these credentials. Also, some psychologists only test for autism in children, not in adults, which can complicate things.

What is your perception of online autism spectrum tests that claim to give a diagnosis?

Paugh: Adults can take these online questionnaires, which can help to assess various symptoms and weed out people who most likely don’t have autism if they don’t identify with specific symptoms, so that they don’t seek out a diagnosis on a professional level. For those that do identify with ASD-associated symptoms, taking these tests may further encourage them to seek that professional confirmation.

Taking these online tests may motivate adults to obtain this professional diagnosis of autism if it is impeding daily living. Other adults who are so high functioning may just want validation and simply to know why they are the way they are.  

When individuals can say they took a specific online test, it helps the provider to know that these individuals did some research and took steps before coming in for a diagnosis. Sometimes, it can be frustrating to learn where people get their information — sources, which may not always be reliable, such as TikTok. Social media and online sources of information are like double-edged swords. These sources help to spread awareness, but people still need to question the reliability and accuracy of their sources of information.

How accurate are these online autism spectrum tests? 

Paugh: These online tests are limited. None of them can give a specific diagnosis for autism. Tests to diagnose autism must be very specific and reliable. It is also important that the person taking the online test is not biased to the questions being asked as this may skew the results.

Do individuals need to take autism spectrum tests more than once (serial testing) to confirm a diagnosis?

Paugh: Usually testing for autism takes place during a single session unless there are significant time limitations that may require the testing to be completed over the course of several sessions. Patients don’t have to keep returning multiple times to take the same tests over and over again to confirm diagnosis.

For me as an on-site nurse practitioner, I only have 30 to 40 minutes with the patient, so I may need to spread out my evaluation over several sessions. Usually during the first session, I am listening more to the parents talking and not really observing the child.

Autism Spectrum Tests

The following autism spectrum tests can help to diagnose ASD and assess the severity of certain characteristics associated with the condition, such as anxiety and sensory processing problems. Selection of the development screening tool depends on the following factors2:

  • location of administration
  • the child’s characteristics, including age, and manifestation of symptoms
  • length of time required to complete the evaluation
  • diagnosis being sought
  • the person completing the evaluation (parents, health care provider, or adults with ASD)
  • specificity and sensitivity of the screening or diagnostic tool to correctly rule out or rule in ASD, respectively

Autism Spectrum Tests for Age 18 Months and Younger

The following tests can help identify various features of ASD in children aged 18 months and younger:

Autism Spectrum Tests for Ages 18 to 24 Months

Many of the tests used in children younger than 18 months also apply to children between 18 and 24 months, including the following:

  • ADOS®-2
  • ABAS®-3
  • DP-4
  • M-CHAT
  • MIGDAS-2
  • SPM-2

Autism Spectrum Tests for Ages 24 Months and Older

While it is possible for providers to accurately diagnose autism in children younger than 24 months, many children are diagnosed later in childhood. These tests include some of those mentioned above as well as the following additional tools:

Autism Spectrum Tests for Any Age

The following tests can be used across the lifespan:

  • ABAS®-3
  • ADOS®-2
  • DP-4
  • MIGDAS-2
  • SPM-2

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