This study is looking at time to diagnostic resolution for children ages 18-36 months with concern of ASD. The main purpose of this research study is to see if the time between when a child aged 18-36 months fails an autism screen or a clinician raises concern and is evaluated is shorter in the primary care practices where the clinicians have been trained to conduct diagnostic evaluations. The training includes use of the Childhood Autism Rating Scale-2, which is validated for use in children 2 and older. The investigators also want to learn more about whether primary care clinicians can accurately evaluate and diagnose young children ages 18-36 months of age with autism spectrum disorder (ASD).

The investigators will conduct a multisite hybrid 1 effectiveness-implementation cluster randomized clinical trial to determine if training Primary Care Clinicians (PCCs) to diagnose autism spectrum disorder (ASD) in young children is an effective strategy for decreasing time from a result indicative of increased likelihood of autism, as determined from a visit in primary care, to diagnostic resolution defined as either making or excluding a diagnosis of autism. The investigators will also assess diagnostic concordance between PCCs and autism experts and facilitators and barriers to implementation of this model. Through pediatric clinics, the investigators will be training primary care clinicians (PCCs) to diagnose ASD as part of an established training program, and will assess their diagnostic accuracy by prospectively enrolling patients at the time of their referral for a confirmatory evaluation by a DBP and comparing their CARS scores and certainty ratings. PCCs will be surveyed about their experiences and feedback about training.

There are 3 cohorts of participants in this study:

Group 1 are primary care clinicians, and will be consented into the study and asked to perform the following activities: complete ASD diagnostic training, either in the immediate intervention or delayed intervention group; continue conducting ASD screening per standard of care; refer patients requiring diagnostic confirmation to one of the study sites, including evaluation on diagnostic accuracy.

Group 2 are staff at a primary care practice where one or more clinician are taking part in the training. They will be given the option to participate in surveys and/or focus groups asking about the impact of this autism assessment training on their practices and workflows.

Group 3 are the parents/legally authorized representatives of patients (age 18-36 months) with a flagged result on an autism screener, distributed per standard of care by their pediatrician/PCC's office. They will be contacted by study staff and verbally consented into the study. They will be asked to complete monthly telephone surveys, for up to 8 months. A subset (referred to as Group 3B) will be referred by their PCCs for confirmatory evaluation at one of the clinical study sites. They will be asked to provide written consent for sharing of their evaluation and relevant information from their medical record.

Inclusion Criteria is at the practice level:

• Are physicians or nurse practitioners.

  -- Currently screen children for ASD at 18 and 24 months using a standard measure

• Willing to have practice randomized and willing to defer PCC training if they are randomized to the control group.

  • Will obtain permission from parents of children 18-36 months with a positive autism screen or clinician concern for research staff to contact them
  • Will attend all training courses, complete all requirements of training, and complete questionnaires that are designed to assess the educational intervention.
  • Will keep a record of all diagnostic evaluations they complete over the study period including those children not referred for diagnostic concordance evaluation if they are randomized to the intervention group

Exclusion Criteria:

- Are not screening children for ASD and standard intervals of 18 and 24 months using a standard meaure.

This will be discussed with Autism Research Consortium Steering Committee

The Developmental Behavior Pediatrician (DBP). To address a secondary aim, a child who is evaluated by a primary care clinician may be seen for a confirmatory ASD evaluation. The DBP will be masked to what the Primary Care Clinician concluded at their ASD evaluation. Once the DBP completes their ASD confirmatory evaluation and concludes their own diagnosis, they will then unmask to the PCC diagnosis.