There is no clear medical test to diagnose the disorder, and neither a blood test nor a brain scan can be a conclusive guide to diagnosing autism spectrum disorder. Although researchers are actively trying intensively to develop such tests and diagnostic scales. Currently, clinicians/clinical specialists in diagnosing autism spectrum disorder rely on observing a child's behavior to determine the presence of the main symptoms of autism: communication difficulties, lack of social interaction and repetitive and restrictive behaviors.

The diagnosis of autism spectrum disorder can be done in two steps, as follows:

DEVELOPMENTAL EXAMINATION:

It is a brief examination that indicates whether the child learns basic skills easily or has difficulty in that.
The doctor asks several questions to the child's parents and the child himself during the examination to monitor how he responds in terms of movement, speech and reaction, where the delay in one of these skills is taken into account. .

FULL DIAGNOSTIC EVALUATION:

It is a comprehensive review, which includes looking at the child's behavior and development and interviewing his family, and also includes a hearing and vision examination, genetic examination, neurological examination, and other medical
tests.

In some cases, the doctor may choose to refer the child and their family to a specialist for further diagnosis and assessment. Specialists who are able to do this type of assessment are:

• Pediatrician
• Neurologist (children's specialty)
• Psychiatrist
• Psychologist
• Autism Diagnostic Observation Table (ADOS): whereby clinicians/clinicians observe children's behavior and how they integrate and interact in different social situations for up to an hour.

More than half of people with autism spectrum disorder have four or more co-existing conditions with autism. The types of conditions associated with autism and how they manifest differ from person to person.

COMMON DISORDERS ASSOCIATED WITH AUTISM SPECTRUM DISORDER

• Medical conditions such as: epilepsy, digestive problems, and sleep disorders.
• Developmental disorders such as: mental disability, language delay. 
  
• Psychological disorders such as: Attention Deficit Hyperactivity Disorder (ADHD), Obsessive Compulsive Disorder, and Depression.
• Genetic disorders such as fragile X syndrome and tuberous sclerosis complex.

Treating autism spectrum disorder is important, as it may help relieve symptoms of autism spectrum disorder and thus improve the quality of life for individuals with autism spectrum disorder. For example, treating sleep problems has behavioral benefits as the number of hours of sleep and quality of sleep can affect the mood of the individual with autism spectrum disorder and the severity of his repetitive behaviors.