Assessment, Screening, and Diagnostic Evaluation
Surveillance versus screening
Developmental surveillance is ongoing clinical observation and parent concern; screening uses validated tools at set ages. The ASQ-3 is a general developmental screen; the M-CHAT-R/F is an autism screen at 18 and 24 months. The Vanderbilt assesses ADHD, the PSC and SDQ screen broadly, and the PHQ-A screens adolescent depression. A positive screen is not a diagnosis.
Diagnostic evaluation
Always begin with hearing and vision testing for language or learning concerns. For global delay, autism, or intellectual disability, first-tier genetic testing includes chromosomal microarray and fragile X testing; MECP2 testing is considered in girls with regression. Neuroimaging is not routine for isolated developmental delay but is indicated with focal neurologic signs, macrocephaly, regression, or seizures. Psychological testing may include Bayley, WISC, and Vineland adaptive scales.
Traps
Do not use an IQ score alone to diagnose intellectual disability. Do not skip audiology because the child “responds to loud sounds.” Do not order extensive metabolic or imaging studies before a careful history and examination. Remember that screening tools vary by age and culture, and interpretation requires clinical judgment.
Worked example
An 18-month-old has no words and does not point. The evaluation should include audiology, the M-CHAT-R/F, and a developmental assessment; genetic testing follows if autism or global delay is confirmed. The rule of thumb: hearing first, then autism screening, then developmental and genetic evaluation when indicated.