First, don't expect anything conclusive at 3 years old. Second, there are no deffinitve "blood tests", brain scans, eeg's nor anything like that. They may do some of that kinda stuff to RULE OUT some things. As with my daughter, her diagnosis gradually evolved. It takes questionaires and observation over a period of time. The may observe him in an observation room (you know, with those mirrors) interacting with a therepist. They may ask you questions. They may ask him questions. They may ask dad questions. Many times the same questions by different people. Maybe you or your son (at 3 i don't know if he will do that, maybe not) can expect some computer questioaires or filling in circles on forms with a number two pencil. Maybe you will see him in a room with a big mirror wth some puzzles or toys. Expect more than one visit. Expect to sign releases of information for every doctor since his birth, Expect some questions about your pregnncy. Did he take those "heel *****" tests at birth? They'll want these records, too.
Do not expect anything immediate.
I can give you a biography of my daughters situation:
At 2 she was identifed as "developmental delay" and got early intervention then
They gave my daughter hearing tests and a BAER (like a mini-eeg) test to RULE OUT anything like hearing loss or auditory nerve damage. They did some kind of genetics testing to RULE OUT fragile x. This took a period of 2 or 3 years. She was observed by the schools leading autism authority consultant. At that point all she could only say "autistic like" at 3 or 4 years. But she did have early intervention services. At 6 we took a slight ADD/ADHD detour (the school took us down that 1 month nightmare). Then we got the PDD nos at the state university clinic center for children. The universiy clinic did the kinda stuff I just described.
That's about all I remember for now.
Testing tools: Lets see... We got the:
ABC Autism Behavior Checklist (a quick and dirty questionaire)
The Rimalnd E4 test ( an 8 page form questionaire)
Autism Diagnosis Interview–Revised (ADI–R) this is fairly recent
Autism Diagnostic Observation Schedule-Generic (ADOS–G)
The ever popular Childhood Autism Rating Scale (CARS)
The Gilliam Autism Rating Scale (GARS)
Most recently now, for higher functioning forms of the autism spectrum we have:
Autism Spectrum Screening Questionnaire (ASSQ), a 27-item checklist. I don'tknow much about it, sorry. I think it's for school age children.
Australian Scale for Asperger's Syndrome this is Tony Attwood's nice questionaire from his book: ASPERGER'S SYNDROME A GUIDE FOR PARENTS AND PROFESSIONALS. He is a REAL expert!
You can find it at OASIS website (a great resource fot AS): www(dot) udel(dot) edu(slash)bkirby(slash)asperger(slash)aspergerscaleAttwood(dot) html
Childhood Asperger Syndrome Test (CAST) Sorry, dunno much about this either.
DISCLAIMER: None of these screening instruments are to be taken as deffinitive indicators of autistic spectrum disorders. These tools can help identify children who might have developmental delays. These are NOT a substitute for a comprehensive diagnostic evaluation by a trained multi disciplinary team of professionals
I missed :
Checklist for Autism in Toddlers (CHAT)
Here is a tool psychologists and psychaitrists use in diagnosing autism.
Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV)
Psychiatric Diagnoses are categorized by the Diagnostic and Statistical Manual of Mental Disorders, 4th. Edition. Better known as the DSM-IV, the manual is published by the American Psychiatric Association and covers all mental health disorders for both children and adults. It also lists known causes of these disorders, statistics in terms of gender, age at onset, and prognosis as well as some research concerning the optimal treatment approaches.