 Most kids get picked up early through questionnaires filled by parents during routine checkups. These screenings start at 18 months and catch those characteristic developmental differences. Remember, most symptoms don't appear before 18 months, but any early delays should be brought to the pediatrician's attention. If red flags are raised, a comprehensive referral is ideal. This expert team, including developmental pediatricians, therapists and psychologists, paints a nuanced picture of the child's strengths and challenges. Unfortunately, not everyone has access to such comprehensive assessments. Therefore, clear diagnostic criteria have been established for pediatricians to utilize. These criteria focus on persistent difficulties in social communication, limited reciprocity, a typical nonverbal communication, repetitive behaviors and functional impairment in daily life.