A. A total of six (or more) symptoms from the three groups, including at least two from Group 1, one from Group 2, and one from Group 3.

Group 1
Qualitative impairment in social interaction, as manifested by at least two of the following:

• Marked impairment in the use of multiple nonverbal behaviors such as eye contact, facial expression, body posture, and gestures to regulate social interaction.
• Failure to develop peer relationships appropriate to the developmental level.
• Lack of spontaneous seeking to share enjoyment, interests, or achievements with others.
• Lack of social or emotional reciprocity.

Group 2
Qualitative impairments in communication, as manifested by at least one of the following:

• Delay in, or total lack of, the development of spoken language.
• In individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others.
• Stereotyped and repetitive use of language.
• Lack of spontaneous pretend play or social imitative play appropriate to the developmental level.

Group 3
Restricted, repetitive, and stereotyped patterns of behavior, interests, and activities, as manifested by at least one of the following:

• Preoccupation with one or more stereotyped and restricted patterns of interest.
• Apparently inflexible adherence to specific, nonfunctional routines or rituals.
• Stereotyped and repetitive motor mannerisms (e.g., hand flapping).
• Persistent preoccupation with parts of objects.

B. Delays or abnormal functioning in at least one of the following areas, with onset before age 3:

• Social interaction.
• Language.
• Symbolic or imaginative play.

C. The disorder is not better explained by Rett Disorder, Childhood Disintegrative Disorder, or Asperger Syndrome.

Clinical Assessment
It is widely recognized that early and appropriately tailored intervention designed specifically for the individual's needs is a crucial step toward integration. Therefore, once suspicions arise, intervention should begin as soon and as quickly as possible. Any individual for whom an autism spectrum disorder is considered very likely is entitled to a comprehensive clinical assessment, medical examination, and a series of supplementary tests. The assessment is important for accurate diagnosis and serves as the foundation for any intervention.

Every clinical assessment should begin by taking a detailed history, including all concerns of the parents, developmental history emphasizing the overall level of development, and medical history. The clinician must identify any points that may be relevant to differential diagnosis. By carefully taking the family history, the examiner should gather information on a range of factors (autism, mild autism traits, intellectual disability, fragile X, tuberous sclerosis) in the nuclear and extended family, as these may indicate the need for chromosomal or genetic testing. Careful observation of the individual's behavior in different settings, both structured and less structured, is required. Examiners must be available to directly observe the individual or view a video recorded at home or in other places they attend (e.g., daycare, school, work).

The assessment should be conducted by a multidisciplinary team with extensive experience in autism and developmental disorders, using internationally validated assessment tools (questionnaires, interviews, observation scales), such as the Autism Diagnostic Interview (ADI), Autism Diagnostic Observation Scales (ADOS), Vineland Adaptive Behavior Scales (VABS), Childhood Autism Rating Scale (CARS), Diagnostic Interview for Social and Communicative Disorders (DISCO), and Behavioral Summarized Evaluation (BSE).

Every child should undergo a comprehensive medical examination, including assessment of visual and auditory acuity, as well as pediatric and neurological examination. To date, there is no laboratory test specifically for autism spectrum disorders. Genetic testing will ultimately be carried out if specific findings are identified during clinical assessment or family history.

The clinical and developmental profile should be completed with a series of psychological and language tests, using appropriate evaluation tools (Psycho-Educational Profile (PEP), and standardized neuropsychological tests such as the Leiter, recent WISC, Reynell, Lowee & Costell's Symbolic Play Test, Peabody Picture Vocabulary Test (PPVT), and others).

It must be emphasized again that the diagnosis of autism should be made solely based on an extensive clinical assessment and should be entirely based on internationally accepted criteria for three serious reasons:

1. To ensure access to appropriate support services and/or to create such services where they are limited or do not exist.
2. To make existing research comparable both in terms of clinical issues and particularly in terms of the effectiveness of the services and treatments provided, which is of great necessity.
3. Every child, whether diagnosed with autism or not, is entitled to the education that meets their specific needs. Loose diagnostic procedures could result in children with autism being excluded from provisions specifically designed for them. It could also encourage the inclusion of individuals with other conditions (such as conduct disorders or learning difficulties), which are not within the autism spectrum. Consequently, these children would not receive the specialized education they deserve while also using the already limited provisions intended for individuals with autism.