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Diagnosing ASD

Diagnosing & Evaluating Autism Spectrum Disorder:

Autism Spectrum Disorder is difficult to diagnose, especially in young children where speech and reasoning skills are still developing. A child may be three years old or older before the full characteristics of ASD are fully apparent. Typically, medical professionals are not trained extensively in diagnosing and evaluating for autism spectrum disorder. Doctors will usually rule out other possibilities before mentioning autism spectrum disorder.


Although ASD is considered a neurological disability, no specific medical test or procedure can confirm a diagnosis of autism. To gather more information that will accurately profile an individual’s strength’s and needs, a variety of tests, assessments, and evaluations should be administered.


It is essential that the process of diagnosing ASD include the assessment and evaluation of an individual’s development, communication, and social skills. Knowing a procedure’s purpose and limitations can help you understand the results more accurately. Usually, professionals assessing children with developmental disabilities look to answer questions such as: What areas of development are affected? Can a specific disorder be recognized? What intervention approaches will be most effective? Evaluation and assessment are ongoing processes. Once a diagnosis has been determined, this process should be repeated periodically to track changes in an individual’s level of functioning and to be sure that the individual’s needs and opportunities are being optimized.


Direct Observation

Direct Observation, Interaction, & Interviews Assessments: Information about a child’s emotional, social, communication, and cognitive abilities is gathered through child-directed interactions, observations of the child in various situations, and interviews of parents and care givers. Parents and family members should be actively involved throughout these assessments. What actually occurs during a specific assessment depends on what information parents and evaluators want to know.



The Autism Diagnostic Observation Schedule (ADOS) and Autism Diagnostic Interview (ADI) and their revisions are the “gold standard” for assessment today. Both have extensive research demonstrating good sensitivity and specificity (meaning that they don’t over or under-diagnose children too much when used appropriately). Both require extensive training, clinical experience, and practice and are used as part of a comprehensive evaluation. To parents, the ADOS may appear to be a jumble of toys and manipulatives the child and evaluator play with, but its items are designed to probe specifically for autistic traits and behaviors, and the evaluator rates the child’s behavior and approach to each item on a scientifically derived algorithm.


Play-based Assessments involve adult observation and partial participation in structured and unstructured play situations that provide information about a child’s social, emotional, cognitive, and communication development. By determining a child’s learning style and interaction pattern through play-based assessments, an individualized treatment plan can be developed.


Functional Assessments aim to discover why a challenging behavior (such as tantruming and head banging) is occurring. Based on the premise that challenging behaviors are a way of communicating, functional assessment involves interviews, direct observations, and interactions to determine what a child with autism or a related disability is trying to communicate through their behavior. Once the purpose of the challenging behavior is determined, an alternative, more acceptable means for achieving that purpose can be developed. This helps eliminate the challenging behavior.


Standardized Testing

Standardized Instruments are formal methods used to determine different levels of cognitive development. Sometimes when a disability is so significant that it affects an individual’s ability to speak, gesture, or move, special adaptations or modifications to existing standardized instruments will be necessary to get an accurate picture of an individual’s abilities.

Intelligence Tests (IQ), such as the Stanford Binet Intelligence Scale, Wechsler Intelligence Scale for Children (WISC), the Differential Abilities Scale (DAS), and their revisions, attempt to determine an individual’s intelligence based on standardized criteria. Scores are highly based on an individual’s communication skills, social skills, and ability to accomplish specific tasks. Individuals with autism and related disabilities may seem uncooperative, stubborn, or withdrawn while in fact the way a test is presented can be too difficult or complicated for them to comprehend. In addition, the individual may not understand the language or expectations of the test which can cause confusion and problem behavior. There are various ways that professionals can adapt a test to try and make it easier for an individual to understand.

Developmental Inventories such as The Vineland Adaptive Behavior Scales, ABAS, and Batelle Development Inventory are examples of standardized tests that measure a child’s general developmental skills including socialization skills and coping skills, and compare them to other children who are typically developing as a reference to come up with age or grade equivalent scores. These scores are obtained based on parent interviews and evaluator observations.

These standardized instruments do not necessarily measure a child’s true abilities, capacities, and unique potential to learn. Many times professionals label a child as “untestable.” This cannot be considered an accurate assumption, for the reasons mentioned above. It is also important to note that these instruments cannot diagnose ASD, and are only one component of a good diagnostic evaluation.


Rating Scales and Screeners

Rating Scales are often provided for parents or teachers to complete. Based on the ratings provided, the scales are scored in a standardized manner to determine if the individual meets the criteria for an autism spectrum disorder. These rating scales may be used to screen individuals for further evaluation, or in conjunction with observations, standardized instruments, and diagnostic interviews or evaluations. The M-CHAT is used to screen for possible ASD in toddler well-child check-ups. The Autism Behavior Checklist, Childhood Autism Rating Scale, Gilliam Autism/Asperger’s Rating Scales, Asperger’s Syndrome Diagnostic Scale and others may be used by schools and medical professionals. These rating scales typically result in a rating of the likelihood that the individual has an autism spectrum disorder, but they are not definitive without additional evaluation.


Medical Tests

Given the variety of theories about the causes of autism and related disabilities doctors may use various medical tests and procedures to help with diagnosis. There is not always a clinical need to do medical tests. Your doctor(s) can recommend when, or if, a test should be done. The following medical tests may help with diagnosis and possibly suggest changes in an intervention or treatment strategy.



Various tests such as an audiogram, typanogram, and the brain stem evoked response can indicate whether a person has a hearing impairment. Audiologists or hearing specialists, have methods to test the hearing of any individual by measuring responses such as turning their head, blinking, or staring when a sound is presented. If a hearing impairment is detected, treatment could involve minor surgery, use of hearing aids, or antibiotics. A hearing test should always be performed when autism is suspected, as hearing loss may cause delays in communication and socialization.


Electroencephalogram (EEG)

An EEG measures brain waves that can show seizure disorders. In addition, an EEG may indicate tumors or other brain abnormalities. Additional tests will be needed to make an accurate diagnosis of these conditions. During an EEG, sixteen small sensors are placed at various locations on the scalp to record brain waves that a neurologist interprets. An EEG may take one to 24 hours depending on the doctor’s goals when ordering the test. If seizure activity is detected, additional testing may be required and various medications could be prescribed.    


Metabolic Screening

Blood and urine lab tests measure how a person metabolizes food and its impact on growth and development. Some symptoms of autism spectrum disorders can be treated with special diets. The following medical tests may help locate neurological factors that can affect typical development and could possibly identify or rule out a cause. Results will probably not change intervention or treatment.


Magnetic Resonance Imaging (MRI)

An MRI involves using magnetic sensing equipment to create an image of the brain in extremely fine detail. The patient lies on a sliding table inside a cylinder shaped magnetic machine and must be still during the procedure. Sometimes patients are sedated in order to complete the MRI.


Computer Assisted Axial Tomography (CAT SCAN)

An x-ray tube rotates around the patient taking thousands of exposures that are sent to a computer where the section of the body that is x-rayed is reconstructed in great detail. CAT Scans are helpful in diagnosing structural problems with the brain.


Genetic Testing

Blood tests look for abnormalities in the genes which could cause a developmental disability.


Asking Questions

Some parents, especially those who have recently learned that their child has a disability, may feel overwhelmed when hearing test results. This is natural, and may stem from their lack of experience with evaluations, or because of a professional’s manner. Remember this is your child. You have the right to ask any questions you want. Asking questions is your first step in beginning to understand more about your child. Learning as much as you can, can have a profound effect on your child’s future. Your CARD coordinator can also help you to understand your child’s results.