Elsevier

Research in Autism Spectrum Disorders

Volume 1, Issue 4, October–December 2007, Pages 330-338
Research in Autism Spectrum Disorders

Norms and cut off scores for the autism spectrum disorders diagnosis for adults (ASD-DA) with intellectual disability

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Abstract

Establishing the cut-off scores for Autism Spectrum Disorder-Diagnostic (ASD-DA) scale for adults with intellectual disability (ID) and autism or PDD-NOS was the primary goal of this investigation. The aim of Study 1 was to determine if the ASD-DA was able to differentiate between adults with ID with and without an autism spectrum disorder, and to determine a total score cut-off for this purpose. The aim of Study 2 was to determine if the ASD-DA was able to differentiate between autism and PDD-NOS in this population. Sensitivity, specificity, and receiver operating characteristics (ROC) were computed for potential cut-off scores and were found to be acceptable. The implications of these data for diagnosing ASD in adults with ID are discussed.

Section snippets

Study 1

The aim of Study 1 was to determine if the ASD-DA can correctly distinguish between adults with ID with and without ASD based on symptoms listed in the DSM-IV (APA, 2000) and ICD-10 (WHO, 1992) guidelines.

Participants

Participants for this study were residents of one of two developmental centers located in the Southeastern region of the United States, which varied in size from 350 to 550 residents. Two hundred and thirty-two individuals were selected for the study with the following diagnoses, profound (n = 176), severe (n = 33), moderate (n = 12), mild (n = 1), or unspecified ID (n = 10). Age of the participants varied from 20 to 80 years. One hundred and fourteen of the participants had a diagnosis of ID and ASD

Discussion

The purpose of Study 1 was to determine if the ASD-DA was able to distinguish between adults with ID with and without comorbid ASD. Further, a second aim was to determine a total cut-off score that would yield optimal sensitivity and specificity for this purpose. Based on the present data, it appears that a total cut-off score of 19 is the optimal score for differentiating between these diagnostic groups.

Study 2

The aim of Study 2 was to examine the utility of the ASD-DA in differentiating between autism and PDD-NOS for adults with ID and ASD.

Method

The methods used in Study 2 were identical to those in Study 1. However, for the 114 participants with an ASD diagnosis based on the DSM-IV/ICD-10 checklist, participants were assigned to two other groups autism (n = 52) or PDD-NOS (n = 62). To qualify for a diagnosis of autism, two separate raters had to endorse at least 1 item on the socialization domain, 2 items on the communication domain, and 1 item in the restrictive/repetitive behavior domain. All other participants having more than 3 total

Discussion

The purpose of Study 2 was to establish cut-off scores for the ASD-DA to distinguish between autism and PDD-NOS in adults with ID. Following the generally accepted notion that scores occur on a continuum, PDD-NOS symptoms were conceptualized as being milder or fewer than those in autism (Matson, in press; Matson & Boisjoli, 2007; Matson et al., 2007). Using a profile analysis of scores for the groups, we were able to generate specific numeric values as potential cut-off scores for two of the

Summary

By using multiple techniques to generate potential cut-off scores and utilizing ROC, the researchers found total cut-off scores on the ASD-DA that optimally differentiated between those with and without ASD. While the range of scores between persons with ID and with and without comorbid ASD may have less variance than seen with the general population, the ASD-DA was able to identify those individuals with an a priori diagnosis of an ASD, displaying good sensitivity and specificity. Using the

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