Laboratory Testing for Developmental Delay, Intellectual Disability, and Autism Spectrum Disorder

Developmental delay (DD) is defined as any significant lag in a child's physical, cognitive, emotional, or social maturity. Intellectual disability (ID) is characterized by broad impairment in cognitive and adaptive functioning, typically with an intelligence quotient (IQ) <70 diagnosed before 18 years of age. A global DD diagnosis often precedes a diagnosis of ID, as cognitive skill or IQ cannot be reliably assessed before age 6. Those with severe DD diagnosed before age 6 are most likely to develop ID.  

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 3 years of age based on parents’ and observers’ identification of abnormal interactions and behaviors.  Routine pediatric screening may identify a child with global delay and spur investigation of the underlying etiology.

Chromosomal microarray (CMA, also referred to as cytogenomic single nucleotide polymorphism [SNP] microarray), is the recommended first-line test for DD/ID or ASD of unknown etiology.    CMA offers the highest diagnostic yield (~15-20%) in individuals with unexplained DD/ID, ASD, and multiple congenital anomalies (MCAs), and is preferred to chromosome analysis (karyotyping).    ,  Multiple groups have made recommendations regarding additional testing for fragile X syndrome (FXS), inborn errors of metabolism (IEMs), X-linked intellectual disability, MECP2-related disorders, PTEN-related disorders, and/or chromosome analysis, depending on clinical findings and family history.     Refer to the Testing for Genetic Syndromes Related to Developmental Delay, Intellectual Disability, and Autism Spectrum Disorder Algorithm for suggested tiered testing approaches.

Tabs Content
Content Review: 
October 2019

Last Update: October 2019