Wednesday, March 30, 2011

IQ and Autism Spectrum Disorders (ASD)

A critical domain of a core assessment battery for ASD is intellectual or cognitive functioning. Establishing the level of cognitive ability is important for both classification and intervention planning purposes. For example, the level of intellectual functioning is associated with the severity of autistic symptoms, skill acquisition and learning ability, and level of adaptive functioning, and is one of the best predictors of long-term outcome. Because the IQs of children with ASD have the same properties as those obtained by other children age 5 years and older, they are reasonable predictors of future educational performance. Thus, an appropriate measure of IQ is considered to be an essential component of the core assessment battery.
The primary goal of conducting an intellectual evaluation includes establishing a profile of the child's cognitive strengths and weaknesses in order to facilitate educational planning and to help determine the presence of any cognitive limitations. Assessment of cognitive strengths and weaknesses is particularly important because of the characteristically uneven profile of skills demonstrated by children with ASD. It is important that the individual test chosen (a) be appropriate for both the chronological and the mental age of the child, (b) provides a full range of standard scores, and (c) measures both verbal and nonverbal skills. Of course, the use of any single score to describe the intellectual abilities of a child with ASD is clearly inappropriate and should never be used for diagnostic confirmation or differential diagnosis of ASD. It also needs to be emphasized that there are no specific cognitive profiles that can “reliably” differentiate children with ASD from children with other disorders. However, when a specific intellectual profile is evident, this can have an important implication for how the child learns best and what intervention activities may be most effective.
A detailed description and application of a core assessment battery can be found in Wilkinson, L. A. (2010). A best practice guide to assessment and intervention for autism and Asperger syndrome in schools.
 
© Lee A. Wilkinson, PhD

Monday, March 7, 2011

Update: Proposed Changes in Criteria for Asperger syndrome


The American Psychiatric Association has updated the proposed draft diagnostic criteria for the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM). Work Group members have proposed a new category of “autism spectrum disorder,” which incorporates the current diagnoses of autistic disorder (autism), Asperger’s disorder, childhood disintegrative disorder, and pervasive developmental disorder not otherwise specified (PDD-NOS). This category reflects members’ conclusion that “a single spectrum disorder” better describes our current understanding about pathology and clinical presentation of the pervasive developmental disorders. The “autistic triad” will now become two:
1)     Social/communication deficits
2)     Fixated interests and repetitive behaviors
The proposed criteria for Autism Spectrum Disorder are:

Must meet criteria 1, 2, and 3:

1. Clinically significant, persistent deficits in social communication and interactions, as manifest by ALL of the following:

a. Marked deficits in nonverbal and verbal communication used for social interaction:

b. Lack of social reciprocity;

c. Failure to develop and maintain peer relationships appropriate to developmental level

2. Restricted, repetitive patterns of behavior, interests, and activities, as manifested by at least TWO of the following:

a. Stereotyped motor or verbal behaviors, or unusual sensory behaviors

b. Excessive adherence to routines and ritualized patterns of behavior

c. Restricted, fixated interests

3. Symptoms must be present in early childhood (but may not become fully manifest until social demands exceed limited capacities)

The rationale for this proposal includes the following.
  • Differentiation of autism spectrum disorder from typical development and other "nonspectrum" disorders is done reliably and with validity; while distinctions among disorders have been found to be inconsistent over time, variable across sites and often associated with severity, language level or intelligence rather than features of the disorder.
  • Deficits in communication and social behaviors are inseparable and more accurately considered as a single set of symptoms with contextual and environmental specificities
  • Delays in language are not unique nor universal in ASD and are more accurately considered as a factor that influences the clinical symptoms of ASD, rather than defining the ASD diagnosis
  • Requiring both criteria to be completely fulfilled improves specificity of diagnosis without impairing sensitivity
  • Providing examples for subdomains for a range of chronological ages and language levels increases sensitivity across severity levels from mild to more severe, while maintaining specificity with just two domains
  • Requiring two symptom manifestations for repetitive behavior and fixated interests improves specificity of the criterion without significant decrements in sensitivity.
  • Unusual sensory behaviors are explicitly included within a sudomain of stereotyped motor and verbal behaviors, expanding the specification of different behaviors that can be coded within this domain, with examples particularly relevant for younger children.
  • The presence, via clinical observation and caregiver report, of a history of fixated interests, routines or rituals and repetitive behaviors considerably increases the stability of autism spectrum diagnoses over time and the differentiation between ASD and other disorders.
  • Reorganization of subdomains increases clarity and continues to provide adequate sensitivity while improving specificity through provision of examples from different age ranges and language levels.



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