Developmental Delay, Intellectual Disability, and Autism Spectrum Disorder Laboratory Testing - Neurocognitive Impairments
Developmental delay (DD) is defined as any significant lag in a child's physical, cognitive, emotional, or social maturity when compared to established norms. Intellectual disability (ID) is classified by broad impairment in cognitive and adaptive functioning, typically with an intelligence quotient (IQ) <70 diagnosed before age 18 years of age. Autism spectrum disorders (ASDs) represent a neurodevelopmental continuum with varying degrees of social impairment, communication limitations, repetitive behaviors, and/or a restricted range of interests. ASDs are typically detected by age 3 based on parents’ and observers’ identification of abnormal interactions and behaviors. Routine pediatric screening may identify a globally delayed child and spur investigation of the underlying etiology. A global DD diagnosis often precedes a diagnosis of ID, as cognitive skill or IQ cannot be reliably assessed prior to age 6. Those with severe DD diagnosed before age 6 are most likely to develop ID.
Laboratory testing should be considered as part of a comprehensive evaluation for individuals with ASD and/or DD/ID (with or without comorbidities) to assist with decisions about treatment and management. Chromosomal microarray (CMA) offers the highest estimated diagnostic yield (~15-20%) in individuals with unexplained DD/ID, ASD, and multiple congenital anomalies (MCAs), and is preferred to karyotyping as the first-tier test. Screening for fragile X syndrome (FXS) and, in some situations, metabolic testing is also recommended. Refer to the Testing for Genetic Syndromes Related to Developmental Delay, Intellectual Disability, and Autism Spectrum Disorder Algorithm for suggested tiered testing approaches.
Last Update: May 2019