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

Wednesday, March 16, 2011

Test Review: The Gilliam Autism Rating Scale: Second Edition (GARS-2)


The GARS-2 is a revision of the widely used Gilliam Autism Rating Scale (1995). It was designed to assist psychologists, teachers, parents, and clinicians in identifying and diagnosing autism in individuals aged 3 through 22 and in estimating the severity of the disorder. The GARS-2 can be individually administered in 5 to 10 minutes and consists of 42 items describing the characteristic behaviors of persons with autism. The items are grouped into three subscales based on two definitions of autism, one from the Autism Society of America and the other from the diagnostic criteria for autistic disorder published in the DSM-IV-TR (American Psychiatric Association, 2000):
  • Stereotyped Behaviors
  • Communication
  • Social Interaction 
The subscale standard scores are summed to produce an Autism Index (mean = 100, SD = 15). Higher standard scores and Autism Indices are indicative of more problematic behavior. Scoring also includes a Probability of Autism classification (Very Likely, Possibly, Unlikely). 

According to the test manual, the second edition reflects several positive changes such as: (a) updated, more clearly described norms; (b) rewriting of some items and the scoring guidelines to improve clarity; and (c) a section that provides specific item definitions and examples for applied behavior analysis and research projects. New to the second edition is a structured interview form for gathering diagnostically important information from the child's parents that replaces the Early Development subscale found in the original version. The GARS-2 was normed on a representative sample of 1,107 persons with autism from 48 states within the United States. Demographic characteristics of the normative sample are keyed to the 2000 U.S. Census data. Few changes were made to GARS test items in developing the GARS-2. The difference between versions exists mostly on the fourth subscale, labeled ‘Developmental Disturbance’ on the GARS and ‘Parent Interview’ on the GARS-2.

Independent studies on the first version of the instrument have indicated less than optimal psychometric properties. For example, research examining the validity of the GARS (1995) consistently found that the scale underestimated the likelihood of children with autism being classified as having autism, indicating low sensitivity, with values ranging from .38 to .53 (Norris and Lecavalier, 2010). Sensitivity is the percentage of true cases correctly identified by a screen; a sensitivity value of .80 is the accepted standard.

A recent study of the validity of the GARS-2 three subscales did not support the subscale structure (Pandolfi, Magyar, & Dill, 2010). The findings suggest that the clinical utility of the scales is limited by factors related to item content and test development procedures and that the Autism Index be interpreted with caution. The Probability of Autism classification also lacks a sound empirical basis and may be subject to misinterpretation. A previous review also notes that although the names of the subscales correspond to the main DSM-IV criteria for Autistic Disorder, the items do not correspond entirely to the behavioral characteristics listed under these criteria or to the traits listed on the website of the Autism Society of America (Garro, 2006). 

There are also questions regarding the normative sample (Norris & Lecavalier, 2010). Group membership was determined via caregiver report of diagnosis and/or school classification. A number of participants (27%) were recruited from the Asperger Syndrome Information and Support website, suggesting that a portion of the sample may have included individuals with other pervasive developmental disorders (PDD/ASD). Although the sample participants should have been diagnosed with autism, there is no information about the specific diagnostic criteria that were in fact used. Diagnosis of participants was not confirmed by the ADI-R, ADOS, or a clinical evaluation. Although the norms are not based upon age, the underrepresentation of older children and young adults also suggests that practitioners need to use caution when using the instrument with individuals from these age groups (Garro, 2006). From a more positive perspective, there is some preliminary support for the validity of the broad-based Autism Index. The content of the GARS-2 also reflects a number of behavioral characteristics that apply to individuals with ASD and may help guide the user in understanding the “autistic triad.” The manual also includes several cautions for the interpretation of results.

According to the manual, the GARS-2 should be administered by professionals who have training and experience in working with individuals with autism such as school psychologists, educational diagnosticians, and autism specialists. Practitioners who are currently using or considering using the GARS/GARS-2 for making an autism diagnosis or assessing symptom severity should exercise caution due to significant weaknesses, including the underidentification of higherfunctioning ASD and questions concerning standardization and norming procedures. Although the GARS-2 may have utility as a general screening or supplementary tool for ASD, it is not recommended it for inclusion as the primary phenotypic instrument in a comprehensive developmental assessment battery for autism (Norris & Lecavalier, 2010; Wilkinson, 2010). 

Garro, A. (2006). Review of the Gilliam Autism Rating Scale-Second Edition. Seventeenth mental measurements yearbook with Tests in Print, Buros Institute of Mental Measurement. Lincoln: University of Nebraska Press.

Gilliam, J. (2006). GARS-2: Gilliam Autism Rating Scale-Second Edition. Austin, TX: PRO-ED.

Lecavalier L. (2005). An evaluation of the Gilliam Autism Rating Scale. Journal of Autism and Developmental Disorders, 35, 795-805.

Norris, M., & Lecavalier, L. (2010). Screening accuracy of level 2 autism spectrum disorder rating scales: A review of selected instruments. Autism, 14, 263-284.

Pandolfi V., Magyar C. I., & Dill C. A. (2010). Constructs assessed by the GARS-2: factor analysis of data from the standardization sample. Journal of Autism & Developmental Disorders, 40, 1118-30. 

Wilkinson, L. A. (2016). A best practice guide to assessment and intervention for autism spectrum disorder in schools. London: Jessica Kingsley Publishers.


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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