Pathophysiology
Clinical meaning
The NP conducts systematic developmental surveillance and screening as a core component of well-child care. The AAP recommends universal developmental screening at 9, 18, and 30 months and autism-specific screening at 18 and 24 months. Screening differs from surveillance: surveillance is ongoing clinical observation at every visit, while screening uses standardized validated tools at specific ages. The Ages and Stages Questionnaire, Third Edition (ASQ-3) is a parent-completed screening tool validated for ages 1-66 months. It assesses five domains: communication, gross motor, fine motor, problem-solving, and personal-social. Each domain has six items scored 'yes' (10 points), 'sometimes' (5 points), or 'not yet' (0 points). Domain scores below cutoff thresholds (specific to each age interval) indicate need for further evaluation. The ASQ-3 has sensitivity of 86% and specificity of 85% for detecting developmental delays. The Modified Checklist for Autism in Toddlers, Revised with Follow-Up (M-CHAT-R/F) is a two-stage parent-report screening for ASD at 18-30 months. The M-CHAT-R has 20 yes/no items; scores of 3-7 require the follow-up interview (M-CHAT-R/F) to reduce false positives. Scores ≥8 indicate high risk requiring immediate referral without...