Autism spectrum disorder in Down syndrome: cluster analysis of Aberrant Behaviour Checklist data supports diagnosis

• Published in: Journal of intellectual disability research Vol. 55; no. 11; pp. 1064 - 1077
• Main Authors: Ji, N. Y., Capone, G. T., Kaufmann, W. E.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-11-2011; Wiley-Blackwell; Wiley Subscription Services, Inc
• Subjects: Aberrant Behaviour Checklist; Adolescent; Autism; autism spectrum disorder; Autism Spectrum Disorders; Autistic spectrum disorders; Behavior Disorders; Behavior Problems; Behavior Rating Scales; Biological and medical sciences; Check Lists; Checklist - statistics & numerical data; Checklists; Child; Child Behavior Disorders - diagnosis; Child Behavior Disorders - epidemiology; Child clinical studies; Child Development Disorders, Pervasive - diagnosis; Child Development Disorders, Pervasive - epidemiology; Child, Preschool; Chromosome aberrations; Clinical Diagnosis; Cluster Analysis; Cognitive Ability; Cognitive impairment; Comorbidity; Comparative Analysis; Developmental disorders; Diagnosis; Diagnostic and Statistical Manual of Mental Disorders; Disability Identification; Disruptive behaviour; Down Syndrome; Down Syndrome - diagnosis; Down Syndrome - epidemiology; Down's syndrome; factor analysis; Female; Humans; Hyperactivity; Infant; Infant, Newborn; Infantile autism; Intellectual Disability; Male; Medical diagnosis; Medical genetics; Medical sciences; Mental Disorders; Multivariate Analysis; Nosology. Terminology. Diagnostic criteria; Pervasive Developmental Disorders; Prevalence; Psychology. Psychoanalysis. Psychiatry; Psychomotor Agitation - diagnosis; Psychomotor Agitation - epidemiology; Psychopathology. Psychiatry; Rating Scales; Self Destructive Behavior; Self-Injurious Behavior - diagnosis; Self-Injurious Behavior - epidemiology; Severe Intellectual Disability; Severe Mental Retardation; Stereotypes; Stereotypic Movement Disorder - diagnosis; Stereotypic Movement Disorder - epidemiology; Symptoms (Individual Disorders); Techniques and methods; Validation studies; Young Adult; Chromosomal aberration; Automatic classification; Trisomy; Questionnaire; Aneuploidy; Aberrant Behavior Checklist Aman Singh; Nosology; Developmental disorder; Criterion; Classification; Diagnosis; autism spectrum disorder; cluster analysis; Child; Human; Preschool age; Diagnostic and Statistical Manual of Mental Disorders; Factor analysis; Psychometrics; Down syndrome; Autism; Concomitant disease; Pervasive developmental disorder; School age; Adolescent; Mental disorder; Aberrant Behaviour Checklist
• ISSN: 0964-2633; 1365-2788
• DOI: 10.1111/j.1365-2788.2011.01465.x

Background  The diagnostic validity of autism spectrum disorder (ASD) based on Diagnostic and Statistical Manual of Mental Disorders (DSM) has been challenged in Down syndrome (DS), because of the high prevalence of cognitive impairments in this population. Therefore, we attempted to validate DSM‐based diagnoses via an unbiased categorisation of participants with a DSM‐independent behavioural instrument.
Methods  Based on scores on the Aberrant Behaviour Checklist – Community, we performed sequential factor (four DS‐relevant factors: Autism‐Like Behaviour, Disruptive Behaviour, Hyperactivity, Self‐Injury) and cluster analyses on a 293‐participant paediatric DS clinic cohort. The four resulting clusters were compared with DSM‐delineated groups: DS + ASD, DS + None (no DSM diagnosis), DS + DBD (disruptive behaviour disorder) and DS + SMD (stereotypic movement disorder), the latter two as comparison groups.
Results  Two clusters were identified with DS + ASD: Cluster 1 (35.1%) with higher disruptive behaviour and Cluster 4 (48.2%) with more severe autistic behaviour and higher percentage of late onset ASD. The majority of participants in DS + None (71.9%) and DS + DBD (87.5%) were classified into Cluster 2 and 3, respectively, while participants in DS + SMD were relatively evenly distributed throughout the four clusters.
Conclusions  Our unbiased, DSM‐independent analyses, using a rating scale specifically designed for individuals with severe intellectual disability, demonstrated that DSM‐based criteria of ASD are applicable to DS individuals despite their cognitive impairments. Two DS + ASD clusters were identified and supported the existence of at least two subtypes of ASD in DS, which deserve further characterisation. Despite the prominence of stereotypic behaviour in DS, the SMD diagnosis was not identified by cluster analysis, suggesting that high‐level stereotypy is distributed throughout DS. Further supporting DSM diagnoses, typically behaving DS participants were easily distinguished as a group from those with maladaptive behaviours.