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Diagnosis & Evaluation

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Overview of Clinical Assessment

Each child requires individualized evaluation and assessment. The manifestations of the core features of autism vary from individual to individual and within the same individual at different developmental stages. Variation in associated cognitive, neurological, and psychiatric features is extensive.

Click here for the Utah Autism Initiative’s publication “Helping You Through the Evaluation Process of Your Child”

The goals of a clinical assessment are to:

  • Recognize children who have developmental signs that could result from autism
  • Determine if the child meets criteria for autism or another ASD while considering differential diagnoses
  • Rule out possible causal medical factors
  • Describe the child’s unique pattern of cognitive strengths and weakness
  • Identify any associated impairing neurological or psychiatric problems
  • Understand how all of the child’s difficulties come together to impair the adaptive functioning of the child and impact his/her family

Click on a heading for more info…


Autism can be diagnosed only when it is considered in the differential diagnosis for a child presenting with a problem or delay in social and/or language development.

Of 1,300 families recently surveyed, the average age at diagnosis of autism was 6 years, despite the fact that most parents felt something was wrong by the time their child was 18 months of age and usually sought medical assistance by the time the child was 2.

The American Academy of Pediatrics recommends that all pediatricians include routine development surveillance of all children during each well-child visit. Practice guidelines also recommend the use of at least one autism screening tool regularly in pediatric practice for children failing routine developmental surveillance. (Source: Filipek: 2000) While none of the readily available screening instruments combine high sensitivity, specificity, and positive predictive value, some can be useful and are described below. Screening tools are not diagnostic tests. Always confirm a positive or negative screening test result with a formal evaluation. Never make a diagnosis with only a screening test.

Early identification of developmental disorders is critical to the well being of children and their families. A revised AAP policy statement entitled, “Identifying Infants and Young Children with Developmental Disorders in the Medical Home: An Algorithm for Developmental Surveillance and Screening,” PEDIATRICS, July 2006 (see page bibliography for reference to full text) provides an algorithm, or a decision tree, as a strategy to support health care professionals in developing a pattern and practice for addressing developmental concerns in children from birth through 3 years of age. The statement recommends that developmental surveillance be performed at every preventive visit and that a screening tool should be administered at 9-,18-, and 24- or 30-month visits and for those whose surveillance yields concerns about delayed or disordered development.

Please see:

For children who are 18 months of age – The CHAT: The Checklist for Autism in Toddlers:

  • Designed to screen for autism at a very young age (18 mos) and to be done twice; children who screen positive at 18 months are screened again 1 month later.
  • Aimed at the primary care setting; it is easy to administer.
  • Readily available here, or download as pdf file (454kb). Click here for more info on CHAT

For children (at least 4 years of age), adolescents, and young adults with or without possible autism – The SCQ: Social Communication Questionnaire by Michael Rutter, M.D., Anthony Bailey, M.D., and Cathy Lord, PhD.

  • The previous name of SCQ was the ASQ (Autism Screening Questionnaire).
  • Originally designed for epidemiologic research and research comparing autism with other clinical groups in terms of autism-like features.
  • Can be used in primary care setting or mailed and completed by parents at home. It takes 10 minutes to complete. The SCQ is a cost effective screening instrument to determine whether an individual should be referred for complete evaluation.
  • Available from Western Psychological Services, or go directly to the SCQ page (cost for each form is about $1.50 when purchased in packs of 20).
  • Click for more info on the SCQ.

When an autism-specific standardized screening tool is not used, the American Academy of Pediatrics recommends at least informal screening by asking particular questions, available on page 7 of Committee: 2001 or, to download as pdf file, click here (pdf 38kb).

Positive Screening- Now What

  • Audiology referral
  • Referral to an early intervention program
  • Reading material for the family
  • Referral for comprehensive evaluation
    • Interdisciplinary clinic (Children with Special Health Care Needs Child Development Clinic)
    • Experienced sub-specialist.

History & Examination

(Source: Filipek: 2000) (Source: Volkmar: 1999)
Pregnancy/Perinatal history
Review history of pregnancy, labor, delivery, and neonatal course may reveal other explanations for presenting symptoms or signs.

Family History
Specifically inquire about a family history of Fragile X, Tuberous Sclerosis, autism, Asperger’s Disorder, and mental retardation.

Current and Past Medical History
Seizures, genetic disorders, encephlopathic events, neurologic disorders. Disorders of attention, mood, anxiety and attachment.

Developmental Evaluation
Developmental surveillance should be a part of all well-child visits from birth through school-age. Evidence-based surveillance tools include:

  • the Ages and Stages Questionnaire (ASQ),
  • the BRIGANCE Screens,
  • the Child Development Inventories, and
  • the Parents’ Evaluation of Developmental Status (PEDS).

If any abnormalities in social development are identified, use the CHAT or SCQ to screen for ASD and obtain a hearing screen. If the child also has mental retardation, follow guidelines for the care and evaluation of children with mental retardation

Physical Exam
Focused on identifying medical conditions associated with autism (see below). In particular, a physical exam should include head circumference, dysmorphology, neurocutaneous abnormalities, and a thorough neurological exam.

Sensory Testing
A formal audiologic evaluation is important for every child with autism. If behavior audiomotry is not definitive, a BAER (brainstem auditory evoked response test) should be performed.

Laboratory Testing
Blood lead screening may be indicated for children with autism and pica or developmental delay. Indications for performing metabolic screening (amino acids, organic acids) include:

  • profound MR
  • cyclical vomiting or lethargy
  • failure to thrive or poor growth
  • motor regression or severe motor delay
  • funny smell

** Note: inborn errors of metabolism do not present with only autism in the absence of other signs and symptoms.

Genetic Testing
Genetic testing is indicated in child with autism who have mental retardation (or in whom mental retardation has not been ruled out), a family history of Fragile X (or undiagnosed mental retardation), or dysmorphic features suggestive of Fragile X. The genetic test ordered would be a karyotype and DNA analysis for Fragile X.

Routine screening with neuroimaging and EEG is not recommended in the absence of abnormal neurological symptoms or signs.

  • The rate of epilepsy ranges from 5% to 38.3% in children with autism. Mental retardation is an important predictor of this co-morbidity. Over 80% of children in one study with IQ<50 had complex or generalized seizures. In children with normal IQ or mild deficits, the incidence of seizures does not exceed that of children with language disorders. There is a bimodal peak of onset of epilepsy in children with autism: one in early childhood and another in adolescence.
  • Children with definite loss of language skills need a sleep deprived EEG to evaluate for the possibility of Landau-Kleffner syndrome (Acquired Epileptiform Aphasia). A child’s language and cognitive development is normal prior to the onset of this disorder.

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Indications for Prompt Referral to an Experienced Clinician for Diagnostic Assessment

  • Screening positive on the CHAT or SCQ
  • No babbling, or pointing or other gestures by 12 months of age
  • No single words by 16 months of age
  • No 2-word spontaneous phrases by 24 months. Spontaneous means not echolalic, i.e., not simply repeating verbatim what another person has said.
  • ANY loss of ANY language or social skills at ANY age

Additional Indications for Consideration of Developmental Evaluation/Diagnostic Assessment


  • lack of pretend play; lack of age-appropriate imaginative play with toys
  • lack of pointing with a finger at things, including objects at a distance
  • lack of social orienting/responsiveness: not looking at you/parent when you or parent talk to him/her or do things with him/her
  • lack of joint attention: lack of integrated eye gaze (between the person and the object), vocalization, and gesture to direct other people’s attention to show things or get help with something.
  • any concern about the child’s social or language development, particularly if the child has unusual interests or repetitive, stereotyped behaviors.

Older Children:

  • social peculiarities or differences from most children; not fitting in
  • inability to carry on a conversation with others
  • lack of interest in other children
  • lack of friends, seemingly because the child does not know what to do
  • any concern about the child’s social or language development, particularly if he/she also has unusual interests and/or repetitive, stereotyped behaviors.


  • lack of friends, seemingly because of lack of interest and/or not knowing what to do socially
  • any concern about the adult’s social or language development, particularly if he/she also has unusual interests or repetitive, stereotyped behaviors.

Medical Conditions Causing Autism Spectrum Disorders

All children with developmental delay and/or autism should have an audiology evaluation by an experienced pediatric audiologist. (link to audiology services) If the child has developmental delay and pica, lead screening is recommended.

  • Autism is idiopathic in about 90% of cases in epidemiologic studies
  • Autism is associated with a definite or probable medical cause in about 10% of cases.

The most common medical causes of autism are:

Tuberous sclerosis (TS)

  • 1-3% of individuals with autism have TS
  • 21-39% of individuals with TS have autism

Signs of TS include:

  • adenoma sebaceum present in 50% by 3 years of age;
  • ash leaf macules on Wood’s lamp exam on trunk, extremities, neck, present in 100% by 2 years of age;
  • shagreen patches on back and buttocks.

Chromosome 15 abnormalities

  • 1-3% of individuals with autism have a maternally inherited duplication of chromosome 15q11-13. This chromosome region is also the critical section involved with Prader-Willi syndrome and Angelman syndrome.
  • Requires FISH (fluorescent in situ hybridization) for detection

Fragile X syndrome

  • 1-2% of individuals with autism have Fragile X; 4% of individual with autism + MR have Fragile X.
  • 80% of individuals with the full Fragile X mutation meet criteria for some PDD; 40% meet criteria for autism.
  • + Fragile X gene

Signs of Fragile X (variable) include:

  • big protuberant ears with soft cartilage;
  • increased length between nose and upper lip;
  • malocclusion – dental crowding;
  • prognathism [abnormal forward projection of the jaw (mandible)] – usually not noted until after puberty;
    enlarged testes – also not noted until after puberty;
  • often increased head circumference.

Other chromosomal disorders and rare genetic syndromes may be associated or causal for ASD. They would likely be found by virtue of and abnormal high-resolution karyotype, with/without dysmorphology (face, head, hands, feet), performed for other reasons. Genetic testing is not indicated at this time for all children with autism

Other medical disorders that may be associated with autism, another ASD, or autistic-like features include:

  • congenital rubella;
  • phenylketonuria;
  • congenital blindness;
  • herpes encephalitis.

Differential Diagnosis

Intellectual Disabilities without autism – Some children meet criteria for both Intellectual Disabilities and autism or PDD-NOS, but most children with Intellectual Disabilities do not have autism.

Specific language disorder – These children have a significant delay in language development and they may have difficulty learning how to read. Impaired language development can also affect a child’s social functioning, but these children do not have the triad of impairments and abnormalities characteristic of ASDs.

Deafness – Even though deaf children may have great difficulty learning to talk, they are usually normal in their use of non-verbal behaviors (e.g. gesture, mime, facial expressions) to communicate.

Selective mutism – Children with selective mutism talk and act normally at home with their families, but they do not talk, i.e., they are functionally mute, in other environments, such as at school.

Reactive attachment disorder – Some children who have been socially and emotionally neglected and maltreated may develop some of the clinical features of ASDs. When they are placed in a nurturing, stimulating environment and are well taken care of, the “autistic” features spontaneously resolve.

Childhood disintegrative disorder – Children with this rare disorder develop normally until 2 years of age or older, but then experience a major deterioration in functioning. The deterioration may involve language, social, and play as in autism, but the deterioration is more severe than in autism and also involves adaptive and motor skills. There is an increased chance that a serious medical disorder is involved.

Rett’s disorder – Rett’s disorder occurs predominantly in girls. It is characterized by normal development until about 5 months of age. Then, the children have a slowed rate of head and brain growth and a severe deterioration in functioning. The deterioration involves motor functioning (i.e., they become unsteady when they walk or sit, loose purposeful hand movements, and develop midline hand stereotypic movements). language and social functioning, and adaptive skills. Mental retardation and seizures usually develop.

Dementia – Children with isolated dementia have a significant decline in intellectual functioning, usually due to a head injury or some other serious medical disorder.

Obsessive compulsive disorder – Many children and adults with ASDs meet criteria for obsessive compulsive disorder (OCD), particularly when they are older, but most children and adults with OCD do not meet criteria for an ASD.

Stereotype habit disorder – This disorder describes children who are mentally retarded and have impairing stereotypic motor mannerisms, but do not meet criteria for an ASD.

Landau-Kleffner syndrome – This syndrome, which is also called acquired epileptic dysphasia, is characterized by normal language development followed by a loss of language. The loss of language is associated with characteristic seizure activity in the temporal lobe of the brain. Children with isolated Landau-Kleffner syndrome do not meet criteria for an ASD. Some children who meet criteria for autism or PDD-NOS may have temporal lobe seizures.

Schizophrenia – Schizophrenia, like autism, is a developmental disorder in which impairments in social and emotional functioning, changes in language functioning, and stereotypes and other unusual behaviors may occur. The onset of schizophrenia is later than autism and usually later than other ASDs. Onset of schizophrenia is rare during childhood and usually occurs during late adolescence or adulthood. The hallmark clinical signs of schizophrenia are hallucinations and delusions. Schizophrenia occurs in about 1% of the general population and rarely in older individuals with ASD. Children with ASDs are not known to be at increased risk of developing schizophrenia.

Schizoid, schizotypal, and avoidant personality disorder – Individuals with these disorders, in isolation, may have some of the social and emotional features seen in some individuals with ASDs (e.g. social avoidance, social anxiety, lack of social interest). Typically they do not meet diagnostic criteria for an ASD.


Committee on Children With Disabilities.
Technical report: the pediatrician’s role in the diagnosis and management of autistic spectrum disorder in children.
Pediatrics. 2001;107:E85. PubMed abstract / Full Text

Filipek PA, Accardo PJ, Ashwal S, Baranek GT, Cook EH Jr, Dawson G, Gordon B, Gravel JS, Johnson CP, Kallen RJ, Levy SE, Minshew NJ, Ozonoff S, Prizant BM, Rapin I, Rogers SJ, Stone WL, Teplin SW, Tuchman RF, Volkmar FR.

Practice parameter: screening and diagnosis of autism: report of the Quality Standards Subcommittee of the American Academy of Neurology and the Child Neurology Society.

Neurology. 2000;55:468-79. PubMed abstract

Volkmar F, Cook, Jr E, Pomeroy J, Realmuto G, Tanguay P, and the Work Group on Quality Issues
Summary of the Practice Parameters for the Assessment and Treatment of Children, Adolescents, and Adults with Autism and Other Pervasive Developmental Disorders.
American Academy of Child and Adolescent Psychiatry; (1999) Accessed on 10/2/04, 2004.

This information is courtesy of The Utah Medical Home Project Team

Identifying Infants and Young Children With Developmental Disorders in the Medical Home: An Algorithm for Developmental Surveillance and ScreeningPublished: PEDIATRICS, July 2006 (Policy Statement)
Authors: Council on Children With Disabilities, Section on Developmental Behavioral Pediatrics, Bright Futures Steering Committee and Medical Home
Initiatives for Children With Special Needs Project Advisory Committee

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