No tests for autism exist. A diagnosis is made by an observation of behavior, coupled with the results of standardized ability tests and medical history. Ability Tests and Behavior Observation
Parents provide data needed to make a diagnosis by completing standardized ability tests, rating their child’s behavior in a number of areas. These tests provide the doctor with information about the child’s developmental history.
In addition to the tests, a parent’s observation of unusual behavior is invaluable. While observation by the examining doctor is possible, the parents’ knowledge of their child’s behavior will surpass anyone else’s observations.
Medical Tests and MRI Scans
Medical tests rule out other conditions. Blood tests, hearing tests, and speech tests are performed. Genetic tests may determine if the child has Fragile X syndrome. Tests will be performed for signs of mental retardation or neurological problems. MRI scans can rule out the possibility of brain disorders. MRI and PET scans may also reveal cellular changes in the brain that are associated with autism.
Autism Spectrum Disorder
If tests and behavior observation indicate possible autism, it will have to be determined if the diagnosis is childhood autism or a different pervasive developmental disorder (PDD). A number of autism-like disorders are grouped together under the heading “Autism Spectrum Disorder.”
The child’s autistic behavior is compared to the different disorders in the autism spectrum disorder. True childhood autism is only one facet of the autism spectrum. A diagnosis of childhood autism requires the child to have significant impairment in three areas:
behavior / interests.
If the child’s autistic behavior does not include all three criteria, or if the behavior is too mild for a diagnosis of childhood autism, a possible diagnosis may be found in other areas of the autism spectrum disorder.
The child’s communication skills develop normally, but social behavior is underdeveloped. Repetitive behavior or interests are also observed. Children with Asperger’s may have above-average to high intelligence.
Childhood Disintegrative Disorder
Children with childhood disintegrative disorder develop normally for the first three years of life. However, after the third year signs of disintegrative disorder appear. Development regresses, including loss of verbal skills, motor skills, and bladder and bowel control. Disintegrative disorder also causes regression in social skills, and the development of autistic-like behavior.
Unlike Asperger’s and disintegrative disorder, which affect either gender, Rett’s disease only affects girls. Rett’s disease is a progressive neurological disease characterized by sudden development regression at six months of age, seizures, and a small head (microcephaly).
Pervasive Developmental Disorder (PDD)
If none of the other autism spectrum disorder diagnoses fit the behavior patterns, the child may be diagnosed with a pervasive developmental disorder (PDD) not otherwise specified. This broad term includes children with mild autistic behavior, sensory integration problems and other pervasive developmental disorders (PDD) that don’t fit the more specific autism spectrum disorder criteria.