Inborn error metabolic screening in individuals with nonsyndromic autism spectrum disorders

To perform metabolic testing on 406 patients (age range 3-22y [mean 6.71, SD 4.15], 343 males and 63 females) with nonsyndromic autism spectrum disorders (ASD) to assess the diagnostic yield. In addition, we reviewed our hospital's clinical database of 8500 patients who had undergone metabolic testing to be identified for inborn errors of metabolism (IEM), and described the characteristics of those with IEM and nonsyndromic ASD.

Neuropsychological evaluation included the Social Communication Questionnaire and Child Behavior Checklist. For metabolic testing/screening, urine samples were analyzed for the diagnosis of cerebral creatine deficiency syndromes, purine and pyrimidine disorders, amino acid metabolism defects, mucopolysaccharidoses, and organic acidurias.

The 406 recruited participants fulfilled the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) criteria of ASD. No biochemical evidence of a metabolic disorder was detected in any of the 406 patients studied. Concerning the retrospective evaluation from the 8500 who had metabolic testing, 464 individuals had a diagnosis of an IEM (394 without the diagnosis of ASD and 70 with ASD diagnosis). Only one individual with IEM had a diagnosis of nonsyndromic ASD at the time of the metabolic study; the metabolic testing had revealed diagnosis of urea-cycle disorder.

Metabolic testing should be considered in the work-up of individuals with syndromic ASD, but metabolic testing is not cost-effective for individuals with nonsyndromic ASD.