Tests

1st tests to order

ASD screening tests

Test
Result
Test

Helpful for gathering information in primary care, but should not be used as a standalone tool to rule in or out a referral for specialist assessment for ASD.[74]

Parental questionnaires, increasingly used as an adjunct to the clinical history. For example: for children, the Social Communication Questionnaire (SCQ), the Childhood Autism Screening Test (CAST), and the Childhood Autism Rating Scale (CARS); for adults, the Social Responsiveness Scale (SRS) and the Autism Screening Questionnaire (ASQ). American Academy of Child and Adolescent Psychiatry: practice parameter for the assessment and treatment of children and adolescents with autism spectrum disorder Opens in new window All are in common use and professionals tend to prefer one rather than another; few comparative data around their utility are available.

Organized by a trained specialist.

Performed with children who are suspected of possibly having ASD.

Not a population screening tool.

Requires interpretation by an ASD clinician.[132][133]

Result

scores over a certain level suggest further evaluation for ASD is warranted; however, some children with ASD score below the instrument’s cut-off

Childhood Autism Rating Scale (CARS)

Test
Result
Test

Principally used as a screening questionnaire among children, but being clinician-rated means that it can also be used to scaffold a diagnostic assessment.[134] Comprises 15 items, each with a 4-point Likert scale.

Result

scores over a certain level suggest further evaluation for ASD is warranted; however, some children with ASD score below the instrument's cut-off

Modified Checklist for Autism in Toddlers (M-CHAT)

Test
Result
Test

This is a parent-completed 23-item questionnaire, principally used as a screening instrument for toddlers suspected of having ASD.[135]

Result

scores over a certain level suggest further evaluation for ASD is warranted; however, some children with ASD score below the instrument's cut-off

Childhood Autism Screening Test (CAST)

Test
Result
Test

This is a parent-completed screening instrument principally used for young children (4 to11 years) suspected of having higher-functioning ASD.[136]

Result

scores over a certain level suggest further evaluation for ASD is warranted; however, some children with ASD score below the instrument's cut-off

Investigations to avoid

hair analysis

Recommendations
Rationale
Recommendations

Do not order hair analysis for “environmental toxins” as a test for ASD.[128]

Rationale

There is no evidence for the clinical efficacy of routine testing of hair for environmental toxins or heavy metals in the assessment of children with suspected ASD.[29]

Hair sample collection and hair analysis methods may not be reliable: for example, chemicals in hair may not be distributed evenly throughout the hair shaft and contaminants, such as dust and hair washing and styling products, may be present. Test results reporting presence of metals in the hair may be a source of anxiety to the patient and their family, and potentially lead to further requests for diagnostic tests.[128]

heavy metal urine test and mineral panel

Recommendations
Rationale
Recommendations

Do not routinely test urine for metals and minerals in children with autistic behaviors.[128]

Rationale

There is no evidence for the clinical efficacy of routine testing of urine for environmental toxins or heavy metals in the assessment of children with suspected ASD.[29]

Toxicologic exposures have not been conclusively associated with the development of autistic behaviors in children. It may be harmful to base treatment on the results of tests for metal and mineral exposure.[128]

Tests to consider

diagnostic questionnaires (e.g., Autism Diagnostic Interview-Revised [ADI-R]; Developmental, Dimensional, and Diagnostic Interview [3di]; Diagnostic Interview for Social and Communication Disorders [DISCO])

Test
Result
Test

Semi-structured, standardized interview undertaken by a trained clinician with the parent, or with someone who knows the person being assessed well.

Gathers behavioral information that helps the clinician make the ASD diagnosis. Not all children and adults with ASD meet criteria.

The instrument algorithms take into account scores from items that gather information about the social, communication, and repetitive domains.

In children whose score reaches cutoff, an ASD diagnosis is likely.[114][137]

Standardized interviews are increasingly used in diagnosis.

Few comparative data around the utility of the diagnostic questionnaires are available.

Result

if the interview score is above the cutoff, a diagnosis of ASD is likely; however, some children with ASD score below the instrument's cut-off

Autism Diagnostic Observational Schedule (ADOS)

Test
Result
Test

A semi-structured, standardized assessment carried out with the child or adult.

Undertaken by a trained specialist.

Administered in a semi-structured way, enabling the clinician to observe behaviors relevant to ASD.

Information helps the clinician make the ASD diagnosis. Not all children with ASD meet ADOS ASD criteria.[113][137]

Standardized observational tools are increasingly used in diagnosis.

Other observational assessments are available; ADOS is the most frequently used observational assessment.

Result

observation assessment score helps to establish whether diagnosis of ASD is likely

skin examination with Wood lamp

Test
Result
Test

Performed where clinically indicated in order to search for hypopigmented macules (suggestive of tuberous sclerosis).[29]

Result

may demonstrate hypopigmented macules in presence of tuberous sclerosis

genetic testing

Test
Result
Test

Fragile X syndrome, chromosomal disorders, and copy number variants and single nucleotide variants, are associated with ASD.

Identification of these disorders has important implications for genetic counseling.[29]

In some regions, such as the UK, targeted genetic testing (e.g., fragile X and clinical microarray testing) is generally offered only to children and adults with intellectual disability, congenital abnormalities, or dysmorphism.[12][104]​ However, in the US and parts of Canada, genetic evaluation (including fragile X testing) is recommended to all families of children with ASD as part of the etiologic work-up.[29] Consensus in the US suggests that targeted genetic testing should also be offered to all children with ASD.[126] However, clinical practice varies considerably. Before ordering a genetic test, ask the patient (or parents/caregivers) about prior genetic testing and review the patient’s medical record.[127]​ Specialist input is typically required for interpreting results, and genetic counselling is helpful to explain the reasons for testing and the subsequent results. Do not order a duplicate genetic test unless there is uncertainty about the existing result (e.g., the result is inconsistent with the current clinical presentation or there is a subsequent change in the test methodology).[127]

Whole exome sequencing is a further option if microarray does not identify an etiology, as guided by the local specialist genetic team, but its yield may not be higher.[125] Practice differs greatly, so clinicians should follow appropriate regional and national guidance on genetic testing. Genetic counseling is often helpful.[29]

Result

may demonstrate abnormality if there is an associated genetic disorder

EEG

Test
Result
Test

Request EEG only if indicated by specific clinical findings in the history or examination (e.g., language regression when aged over 3 years following typical development, or evidence of a possible seizure disorder).[12][29][104]

Result

may be normal or abnormal depending on the presence of any associated or comorbid conditions

MRI brain

Test
Result
Test

Request MRI only if indicated by specific clinical findings in the history or examination (e.g., language regression when aged over 3 years following typical development).[29]

Result

may be normal or abnormal depending on the presence of any associated or comorbid conditions

audiology

Test
Result
Test

Consider if hearing loss causing language delay has not been excluded. Hearing loss may also present as behavioral problems or inattention in children.[29]

Result

may be abnormal if hearing loss is causing language delay

specific testing for genetic disorders (e.g., MECP2 deletion)

Test
Result
Test

The diagnostic yield for other tests is low.

Biochemical or genetic tests should be undertaken if a specific disorder is suspected following the clinical history or examination (e.g., M-methyl-CpG binding protein [MECP2] deletion should be tested for in girls with ASD, clinical Rett syndrome features, and regression).[29]

Result

may be normal or abnormal depending on underlying condition

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