Additional laboratory tests may be done under specific circumstances. These tests include:

• Chromosomal analysis, which may be done if mental retardation is present or there is a family history of mental retardation. For example, fragile X syndrome, which causes a range of below-normal intelligence problems as well as autistic-like behaviors, can be identified with a chromosomal analysis.
• An electroencephalograph (EEG), which is done if there are symptoms of seizures, such as a history of staring spells or if a person reverts to less mature behavior (developmental regression).
• A magnetic resonance image (MRI), which may be done if there are signs of differences in the structure of the brain.

Early detection

All health professionals who see infants and children for well child visits should watch for early signs of developmental disorders. Developmental screening tools, such as the Ages and Stages Questionnaire or the Modified Checklist for Autism in Toddlers (M-CHAT), can help assess behavior.

If a health professional discovers the following obvious signs of developmental delays, the child should immediately be evaluated:³

• No babbling, pointing, or other gestures by 12 months
• No single words by 16 months
• No 2-word spontaneous phrases by 24 months, with the exception of repeated phrases (echolalia)
• Any loss of any language or social skills at any age

If there are no obvious signs of developmental delays or any unusual indications from the screening tests, most infants and children do not need further evaluation until the next well child visit.

However, children who have a sibling with autism should continue to be closely monitored, because they are at increased risk for autism and other developmental problems. In addition to the evaluations at well child visits, these children should undergo testing for language delays, learning problems, poor socialization skills, and any symptoms that might suggest they have anxiety or depression.³

When socialization, learning, or behavior problems develop in a person at any time or at any age, he or she should also be evaluated.