Investigations
1st investigations to order
ASD screening tests
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.[75]
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.
Organised by a trained specialist.
Performed with children who are suspected of possibly having ASD.
Not a population screening tool.
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
Principally used as a screening questionnaire among children, but being clinician-rated means that it can also be used to scaffold a diagnostic assessment.[132] 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
This is a parent-completed 23-item questionnaire, principally used as a screening instrument for toddlers suspected of having ASD.[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 Screening Test (CAST)
Test
This is a parent-completed screening instrument principally used for young children (4 to11 years) suspected of having higher-functioning ASD.[134]
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 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
Semi-structured, standardised interview undertaken by a trained clinician with the parent, or with someone who knows the person being assessed well.
Gathers behavioural 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][135]
Standardised 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
A semi-structured, standardised assessment carried out with the child or adult.
Undertaken by a trained specialist.
Administered in a semi-structured way, enabling the clinician to observe behaviours relevant to ASD.
Information helps the clinician make the ASD diagnosis. Not all children with ASD meet ADOS ASD criteria.[113][135]
Standardised 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
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
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 counselling.[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 aetiological workup.[29] Consensus suggests this test should be undertaken in all children with ASD.[126] Clinical practice about which children should receive a microarray varies considerably at a regional and national level. One suggestion is that children with dysmorphism and intellectual disability be tested, but some services offer testing to all children with ASD.[50] Whole exome sequencing is a further option if microarray does not identify an aetiology, 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 counselling is often helpful.[29]
Result
may demonstrate abnormality if there is an associated genetic disorder
EEG
Test
Neither EEG nor MRI should be carried out unless 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).[29]
Result
may be normal or abnormal depending on the presence of any associated or comorbid conditions
MRI brain
Test
Neither EEG nor MRI should be carried out unless 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
Considered if hearing loss causing language delay has not been excluded. Hearing loss may also present as behavioural 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
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
Use of this content is subject to our disclaimer