Diagnosis
Autism Society of America:

An accurate diagnosis must be based on observation of the individual’s communication, behavior, and developmental levels. However, because many of the behaviors associated with autism are shared by other disorders, various medical tests may be ordered to rule out or identify other possible causes of the symptoms being exhibited. At first glance, some persons with autism may appear to have mental retardation, a behavior disorder, problems with hearing, or even odd and eccentric behavior. To complicate matters further, these conditions can co-occur with autism. However, it is important to distinguish autism from other conditions, since an accurate diagnosis and early identification can provide the basis for building an appropriate and effective educational and treatment program.

Early Diagnosis
Research indicates that early diagnosis is associated with dramatically better outcomes for individuals with autism. The earlier a child is diagnosed, the earlier the child can begin benefiting from one of the many specialized intervention approaches.

Diagnostic Tools
The characteristic behaviors of autism spectrum disorders may or may not be apparent in infancy (18 to 24 months), but usually become obvious during early childhood (24 months to 6 years).

As part of a well-baby/well-child visit, your child’s doctor should do a “developmental screening” asking specific questions about your baby’s progress. The National Institute of Child Health and Human Development (NICHD) lists five behaviors that signal further evaluation is warranted:

• Does not babble or coo by 12 months
  
• Does not gesture (point, wave, grasp) by 12 months
  
• Does not say single words by 16 months
  
• Does not say two-word phrases on his or her own by 24 months
  
• Has any loss of any language or social skill at any age.

Having any of these five "red flags" does not mean your child has autism. But because the characteristics of the disorder vary so much, a child showing these behaviors should have further evaluations by a multidisciplinary team. This team may include a neurologist, psychologist, developmental pediatrician, speech/language therapist, learning consultant, or other professionals knowledgeable about autism.

Screening Instruments
While there is no one behavioral or communications test that can detect autism, several screening instruments have been developed that are now being used in diagnosing autism:

1. CARS rating system (Childhood Autism Rating Scale), developed by Eric Schopler in the early 1970‘s, is based on observed behavior. Using a 15-point scale, professionals evaluate a child's relationship to people, body use, adaptation to change, listening response, and verbal communication.
   
   
2. The Checklist for Autism in Toddlers (CHAT) is used to screen for autism at 18 months of age. It was developed by Simon Baron-Cohen in the early 1990s to see if autism could be detected in children as young as 18 months. The screening tool uses a short questionnaire with two sections, one prepared by the parents, the other by the child's family doctor or pediatrician.
   
   
3. The Autism Screening Questionnaire is a 40 item screening scale that has been used with children four and older to help evaluate communication skills and social functioning.
   
   
4. The Screening Test for Autism in Two-Year Olds is being developed by Wendy Stone at Vanderbilt and uses direct observations to study behavioral features in children under two. She has identified three skill areas that seem to indicate autism - play, motor imitation, and joint attention.

Consulting with Professionals
Whether you or your child’s pediatrician is the first to suspect autism, your child will need to be referred to someone who specializes in diagnosing autism spectrum disorders. This may be a developmental pediatrician, a psychiatrist or psychologist, and other professionals that are better able to observe and test your child in specific areas.

This multidisciplinary assessment team may include some or all of the following professionals (they may also be involved in treatment programs):

• Developmental pediatrician – Treats health problems of children with developmental delays or handicaps.
  
  
• Child psychiatrist – A medical doctor who may be involved in the initial diagnosis. He/she can also prescribe medication and provide help in behavior, emotional adjustment and social relationships).
  
  
• Clinical psychologist – Specializes in understanding the nature and impact of developmental disabilities, including autism spectrum disorders. May perform psychological and assessment test, as well as help with behavior modification and social skills training.
  
  
• Occupational therapist – Focuses on practical, self-help skills that will aid in daily living such as dressing and eating. May also work on sensory integration, coordination of movement, and fine motor skills.
  
  
• Physical therapist – Helps to improve the use of bones, muscles, joints, and nerves to develop muscle strength, coordination and motor skills.
  
  
• Speech/language therapist – Involved in the improvement of communication skills, including speech and language.
  
  
• Social Worker – May provide counseling services or act as case manager helping to arrange services and treatments.