Diagnosing autism: the M-CHAT test, assessment steps and who diagnoses it

10Who diagnoses autism?

Diagnosing autism is the work of a team more than the verdict of one doctor in one visit. The CDC notes that the specialist assessment may be done by a developmental pediatrician, a child psychologist, a speech-language pathologist, an occupational therapist, or a group of them.

The American Psychiatric Association adds the child neurologist and the child and adolescent psychiatrist. In Egypt the path often starts with the pediatrician, then child development clinics or child psychiatry at university and private hospitals. What matters is that the specialist has real experience with autism and does not rely only on a quick look or a questionnaire.

11When can autism be diagnosed?

According to the CDC, autism can sometimes be detected at 18 months or younger, and at age 2 an experienced specialist's diagnosis can be reliable. Even so, many people are not diagnosed until adolescence or adulthood, and miss out on early support. The American Academy of Pediatrics recommends an autism-specific screening at the 18- and 24-month visits, alongside ongoing developmental monitoring at every visit.

12The M-CHAT autism test: what is it and how is it used?

The best-known screening tool for toddlers is the M-CHAT-R/F, the “Modified Checklist for Autism in Toddlers, Revised with Follow-Up.” It is a questionnaire that parents fill out, with 20 yes-or-no questions about everyday behaviors such as pointing, eye contact and play; it takes less than 5 minutes and is designed for children aged 16 to 30 months. If needed, it is followed by a second part, a follow-up interview conducted by a specialist to clarify the answers.

In the validation study of more than 16,000 children, 47.5% of those whose results stayed positive after follow-up were diagnosed with autism, and 94.6% of them had a developmental delay or a concern worth attention. This means a positive result almost always signals that the child needs assessment and support, even if the child is not autistic. For older children, the Social Communication Questionnaire (SCQ) is used, as the MSD Manual notes.

13Steps in the diagnostic assessment of a child

1. Step one
   Interview and developmental history

   Questions about pregnancy and birth, when the child started talking and walking, and what the family notices at home.

2. Step two
   Observation and structured play

   The specialist observes the child's communication, play and interaction, and may use a structured tool such as ADOS-2.

3. Step three
   Medical and hearing exam

   A physical exam and a hearing test to rule out hearing loss as a cause of delayed speech, and lab tests when needed.

4. Step 4
   Language and ability assessment

   An assessment of speech and language, and of cognitive and motor abilities, and gathering reports from nursery or school.

5. Step 5
   Report and support plan

   A report explaining the diagnosis, strengths, needs and co-occurring conditions, and the support that follows.

These steps summarize what the NHS and CDC describe, and they may take place in one long visit or several visits. A member of the team may also visit the school to observe the child in class and at break times.

14Diagnostic tools and accepted criteria

• DSM-5-TR criteria: difficulties in the three social areas, and at least two repetitive or sensory behaviors, present since early childhood, to a degree that disrupts life.
• The ADOS-2: a structured observation session in which the specialist interacts with the child or adult through specific activities and questions, usually conducted by psychologists or developmental doctors.
• The CARS-2: a rating scale for the severity of autistic traits, with a version for those whose language and cognitive abilities are higher.
• Intelligence and ability tests: they help in understanding strengths and weaknesses and in planning education, and a child's performance on practical tasks may be better than on verbal ones.

15Is there a lab test or scan to diagnose autism?

No. Cleveland Clinic affirms that there are no blood or urine tests or biomarkers that diagnose autism. However, the MSD Manual recommends genetic and metabolic tests after diagnosis to look for treatable or inherited conditions such as fragile X syndrome. These tests look for a cause; they neither prove nor rule out autism. An EEG may be requested if episodes resembling seizures appear.

16Conditions that must be ruled out or found alongside it

17Diagnosing autism in adults

The NIMH says diagnosing adults is often harder, because some autistic traits overlap with anxiety or ADHD, and it can be done by a psychiatrist, psychologist or neuropsychologist with experience in autism. The NHS describes what it may include: self-report questionnaires, questions about childhood, work and relationships, talking with someone who knew you as a child and someone who knows you now, and reviewing old school reports. A diagnosis later in life helps many people make sense of years of unexplained difficulties.

18Online autism tests: are they enough?

• They are screening tools, not diagnosis: they point to a possibility that needs assessment, they do not measure onset in childhood, and they do not rule out similar conditions.
• They may reassure you wrongly: so you postpone an assessment your child needs during the most valuable years for intervention.
• They may also frighten you needlessly: since many behaviors in young children are temporary or have other causes.
• The right alternative: write down your observations and record short videos of the child's behavior, and show them to the specialist.

After diagnosis, the most important stage begins. Learn about the options on the autism treatment page, and about the signs in detail on the autism symptoms page.