Recent advances in the diagnostic paradigms of ASD
DSM-IV and DSM-5 criteria. In an attempt to enhance diagnostic reliability and validity, the DSM-5 task force and work groups have proposed various changes in the nosology of autistic disorders and related disorders in DSM-5. First, “disorders usually first diagnosed in infancy, childhood, or adolescence” in DSM-IV will be renamed “neurodevelopmental disorders.”
Second, the previously discrete diagnoses under pervasive developmental disorders (including autistic disorder; Asperger disorder; childhood disintegrative disorder; and pervasive developmental disorder, not otherwise specified) will be consolidated into a single diagnostic category of ASD. This change is supported by a recent study demonstrating that clinical distinctions among categorical diagnostic subtypes of ASDs were not reliable across sites with well-documented fidelity using standardized diagnostic instruments.33
A third change is that DSM-IV describes 3 defining dimensions of behavior:
- • Deficits in social reciprocity
- • Deficits in communication
- • Presence of restricted, repetitive behaviors and interests
Fourth, “play and imagination” and “stereotyped and repetitive use of language” are no longer in DSM-5. However, sensory abnormalities are now taken into account in DSM-5 under RRBs. Lastly, the age of onset of symptoms (before age 3) required in DSM-IV is replaced by a more flexible criterion of “early childhood” in DSM-5.
These changes have received many reactions from the media, families, and clinical and scientific communities. Using data archived from a field trials study for DSM-IV, a recent study reported that the proposed DSM-5 criteria could substantially alter the composition of the autism spectrum and exclude a significant portion of high-functioning individuals and those with ASD other than autistic disorder.34 The DSM-5 work group for neurodevelopmental disorders pointed out that this study used data from DSM-IV field trials and therefore the findings could not be generalized to apply to DSM-5.35 Data from phase 1 field trials of DSM-5 suggest that the criteria adequately captured those with clinical and subthreshold autistic presentations and that the diagnostic fit was stable across age and sex.36 Another study found that relaxing the DSM-5 criteria by requiring one less symptom criterion in RRB increased sensitivity with minimal reduction in specificity.37
Whether the proposed changes will affect both diagnosis and services covered by insurance remains to be seen. The question of whether services should be based on specific diagnoses as opposed to clinical needs is raised. Other proposed changes in the nosology of neurodevelopmental disorders in DSM-5 are summarized in Table 3.
Diagnostic assessment and genetic testing. Diagnosing ASDs using clinical criteria is only part of a full diagnostic assessment. ASDs may be diagnosed in conjunction with a neurodevelopmental syndrome or independently as idiopathic autism. The presence of a neurodevelopmental or genetic syndrome may prompt clinical testing for autism, and similarly, the diagnosis of an ASD may prompt genetic testing for an underlying genetic syndrome.
In 2010, the International Standard Cytogenomic Array Consortium published a consensus article recommending array comparative genomic hybridization (aCGH), also known as chromosomal microarray, as the first-line tier of testing for any individual with an ASD.38 This recommendation was supported shortly after by a paper published by the Autism Consortium.39 Currently, studies suggest that genetic testing with aCGH can uncover genetic variations in up to 20% of cases of autism.40 Variations are more likely to be found in those with intellectual delay, physical dysmorphisms, and other congenital anomalies or medical disorders. It should be noted that aCGH alone will not identify all genetic variations associated with ASDs. For example, testing for fragile X syndrome, sequencing for certain genes, metabolic testing for metabolic disorders, and other laboratory tests may be considered in conjunction with aCGH.
Screening and early detection. Because early behavioral interventions are a key aspect of treatment in ASDs, early diagnosis is an important area of research. Developing screening tools and tests to improve early detection is an ongoing area of investigation in the field. Currently, the American Academy of Pediatrics recommends screening all toddlers at 18 and 24 months.41
A brief parent questionnaire, the Communication and Symbolic Behavior Scales Developmental Profile Infant-Toddler Checklist, accurately identifies autism or other developmental delays in approximately 75% of 1-year-olds at their 1-year pediatric checkup.42 Other investigators are seeking to identify unique patterns to identify ASDs using biological tests such as MRI and electroencephalography.43-45 Questionnaires or screens such as these may improve the rate of identification and referral and lead to earlier treatments.