Additional Tests: The Role of Hearing, Vision, Genetic Tests, and EEG

Although an ASD diagnosis is a behavioral one, a comprehensive assessment should also include certain additional tests to rule out and identify medical conditions that could contribute to social communication difficulties or occur alongside ASD. In this chapter, we'll look at when and why each of these tests is ordered.

Hearing Assessment

Hearing loss can lead to language delay and social withdrawal, and it can be confused with ASD or occur alongside it. For this reason, it is standard practice to do an audiological (hearing) assessment early in the diagnostic process for every child with developmental delay or suspected ASD. In young children where behavioral tests can't give reliable results, this assessment can also be done with objective methods such as otoacoustic emissions or the auditory brainstem response (ABR).

Vision Assessment

Vision problems can similarly contribute to, or be confused with, difficulties in social interaction and eye contact. A full eye examination should be part of the assessment process to rule out refractive errors, strabismus, and, more rarely, vision-related neurological conditions.

Genetic Tests

As we discussed in Chapter 14, a significant portion of children with ASD may have an underlying identifiable genetic cause. Current guidelines recommend considering chromosomal microarray analysis and Fragile X testing in every child diagnosed with ASD; in cases with pronounced accompanying unusual facial features, severe intellectual disability, a history of seizures, or a family history, more extensive genetic tests such as whole-exome sequencing may also come into play. These tests should be ordered alongside genetic counseling, and the results should be reviewed with the family in understandable language.

The Role of EEG: When Is It Ordered?

A routine EEG is not a standard test for diagnosing ASD; that is, an EEG doesn't automatically need to be done for every child with suspected ASD. However, an EEG assessment should definitely come into play in the following situations:

• Clinically suspected signs of seizures (zoning out, a sudden pause, meaningless repetitive movements, episodes with a change in awareness)
• Pronounced developmental regression, especially a sudden and clear loss of language and social skills (to rule out rare epileptic conditions such as Landau-Kleffner syndrome)
• Children at high risk of epilepsy because of a known genetic syndrome (such as tuberous sclerosis)

Outside of these situations, a routine, "screening" EEG is not recommended; because in children with ASD — even without clinical seizures — some electrical abnormalities can be found on EEG, and the clinical significance of these findings must be carefully interpreted by an experienced pediatric neurologist; not every abnormal EEG finding requires treatment.

When to Seek Advice

If you notice "zoning out" or unexplained behavioral freezes in a child with ASD, rather than accepting it as a routine autism feature, be sure to report it to a pediatric neurologist and request an EEG assessment (see Chapter 13).

Metabolic and Other Laboratory Tests

If there are specific clinical clues (poor growth, recurrent vomiting, episodes of lethargy, an unusual body odor, ASD together with severe intellectual disability), additional blood and urine tests may be ordered to rule out rare metabolic diseases. But these tests are done selectively, based on clinical suspicion — not routinely in every child with ASD.

Did You Know? — Closing Part Three

An ASD diagnosis is a clinical diagnosis made by bringing together the history and direct behavioral observation; no single test proves it.

Screening tools (like the M-CHAT-R/F) don't make a diagnosis; they only identify who should be referred for a comprehensive assessment.

The ADOS-2, ADI-R, and Vineland-3 are gold-standard tools that complement one another; none is sufficient on its own.

Cognitive assessment in nonverbal children must be supported with nonverbal/performance-based tests.

Hearing and vision assessment is a standard part of every diagnostic process.

Genetic tests and EEG are ordered selectively based on clinical clues, not routinely.

The Next Step

In this part, we've looked in detail at the path from concern to a definite diagnosis — history, observation, screening, standard scales, and additional tests. In Part Four, we move on to the most important step after a diagnosis is made: from the general principles of treatment to behavioral approaches, from speech and occupational therapy to medications and complementary approaches, we'll examine all the support options available for your child, along with their levels of evidence.