Autism diagnosis involves two stages, states Psych Central: an initial screening stage during routine health checks, and a more formally evaluative second stage. First-stage checklists include the Checklist of Autism in Toddlers and its improved derivatives. Second-stage checklists include the Childhood Autism Rating Scale.
Standard pediatric health check-ups typically include developmental screening in which parents go through an autism screening checklist, according to the Centers for Disease Control and Prevention. The Communication and Symbolic Behavior Scales' Infant Toddler Checklist is one such parent-completed autism checklist, screening toddlers up to the age of 24 months.
The Checklist for Autism in Toddlers, also known as CHAT, is another parent-completed autism checklist suitable for children aged 18 to 24 months, according to the CDC. The Modified Checklist for Autism in Toddlers, also known as M-CHAT, is an improved version of the Checklist for Autism in Toddlers, and is suitable for toddlers aged 16 to 30 months. Released in 2013, the Modified Checklist for Autism in Toddlers-Revised, also known as the M-CHAT-R, is the most recent version of this series of checklists, with a lower false positive rate and higher sensitivity than the Modified Checklist for Autism in Toddlers. It is also suitable for ages 16 to 30 months.
The second stage of autism diagnosis is carried out by specialists, according to Psych Central. An example of a formal diagnostic checklist used during this stage is the Childhood Autism Rating Scale, also known as CARS. It is suitable for children over the age of 2, and gathers information based on observation of the child and the parents' answers. The scale is based on deviation from typical behavior of children of the same age.