This study involves sample collection to identify biomarkers relating to Autism Spectrum Disorder(ASD) in the saliva of children who are between the ages of 18 months to 6 years and 11 months. Participants will at each timepoint have a non-invasive saliva swab collected and complete a brief demographic and medical history questionnaire as well. Children in the pediatric/provider setting who will receive a referral for an ASD diagnosis because they were determined to have a suspicion of developing ASD will be enrolled in the study. Children will also be enrolled in the specialist evaluation setting where they will receive a DSM-5 diagnosis. A subset of both enrollment cohorts will also be followed up with at a third time point in which their diagnosis will be confirmed, and information about any ongoing treatment will be gathered.

Inclusion Criteria:

• 18 through 83 months old

• The study will include children "at risk" for ASD as defined by meeting one or more of the following criteria:

  • flagged positive on a developmental screening tool (see below for assessment cut off scores)
  • the child has a biological sibling with ASD
  • Significant provider concern based on parent report noted in the child's medical chart at the time of the appointment.
  • Significant parental concern

Exclusion Criteria:

• Feeding tube dependence
• Active periodontal disease
• Confounding neurological condition (i.e. cerebral palsy, epilepsy)
• Sensory impairments (i.e. blindness or deafness)
• Acute illnesses (i.e. upper respiratory infection)
• Currently on antibiotics
• Had taken antibiotics within the previous 30 days
• Wards of the state

Participants will be enrolled at pediatric offices, as well as specialist evaluation centers who are deemed at-risk for Autism Spectrum Disorder.