“Diagnosing ASD can be difficult since there is no medical test, like a blood test, to diagnose the disorders. Doctors look at the child’s behavior and development to make a diagnosis.
ASD can sometimes be detected at 18 months or younger. By age 2, a diagnosis by an experienced professional can be considered very reliable.1 However, many children do not receive a final diagnosis until much older. This delay means that children with ASD might not get the early help they need.”
Centers for Disease Control and Prevention-CDC