Pervasive Developmental Disorder Workup

Updated: Oct 19, 2018
  • Author: Sufen Chiu, MD, PhD; Chief Editor: Caroly Pataki, MD  more...
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Approach Considerations

Fragile X DNA testing should be the first test ordered.

If the history or physical findings suggest additional concerns, consider the following:

  • High-resolution cytogenic studies with fluorescence in situ hybridization (FISH) testing for Prader-Willi, Angelman, and Williams syndromes

  • Creatine phosphokinase measurement - To rule out muscular dystrophy

  • Determination of lead level - To rule out lead poisoning

  • Urine organic acid test

  • Plasma amino acid test

  • Lactate and/or pyruvate test - To rule out mitochondrial disorders

  • Serum ammonia test - To rule out urea cycle defects

  • Test for very long fatty acids - To rule out peroxisomal disorders

  • Test of thyroid-stimulating hormone - To rule out hypothyroidism

  • Gene sequencing for MECP2 (Rett's Syndrome)

  • Polymerase Chain Reaction (PCR) for Fragile X syndrome

Hearing testing

A hearing test should be administered. [35] A hearing test should be performed by a pediatric audiologist and should be repeated even if the test results were normal at birth. Testing of children usually requires the presence of 2 pediatric audiologists.


DNA Testing and High-Resolution Cytogenetic Studies with FISH

Fragile-site mental retardation 1 gene (FMR1) deoxyribonucleic acid (DNA) testing for Fragile X syndrome and premutation involvement as indicated. [21]  

Genetic testing should be considered, even if no obvious dysmorphic features are found in the physical examination. Many individuals with Fragile X syndrome appear physically normal (see the image below).

Young child with fragile X syndrome who does not h Young child with fragile X syndrome who does not have obvious dysmorphic features. Courtesy of Randi J Hagerman, MD, FAAP.

Gene Sequencing for MECP2 (Rett's Syndrome)

High-resolution cytogenetic studies with FISH are used to test for 15q duplication, which has been found in 3%–5% of individuals with autism. [7]


Comparative Genomic Hybridization

Comparative genomic hybridization (CGH) is now often recommended to identify a greater number of subtle cytogenetic abnormalities in pervasive developmental disorder (PDD). Up to 20% of individuals with a ASD may have these slight abnormalities. [6]



Imaging Studies

Brain magnetic resonance imaging (MRI), but not head computed tomography (CT) scanning, may be helpful in the clinical assessment of global developmental delay, as the Practice Committee of the Child Neurology Society outlined in 2003. [36, 37]

Functional MRI, magnetic resonance spectroscopy (MRS), positron emission-tomography (PET) scanning, and single photon CT (SPECT) scanning remain research tools. MRS is growing in promise as a tool in screening for conditions such as a deficiency in the creatine transporter gene. [38]

Also see PET Scanning in Autism Spectrum Disorders.



Results are abnormal in 25% of children with ASD.

Results are abnormal in all children with Rett syndrome.

Results can be diagnostic for children with Landau-Kleffner syndrome (LKS), because seizure activity in the brain speech centers often causes this rare disorder.


Psychological and Neuropsychological Testing

In older children, testing may help distinguish atypical ASD or pervasive developmental disorder (PDD) not otherwise specified from a mood disorder, early presentation of schizophrenia, or schizotypal personality disorder. [39]

Testing may reveal verbal and nonverbal learning disabilities.