2009-03-30

The Childhood Autism Rating Scale (CARS) as a reference for diagnosis of autism



Abstract

The Childhood Autism Rating Scale (CARS) is an instrument for screening and diagnosis of autism. The present study performed is to assess the discriminative power of CARS in distinguishing between the autism and other troubles, as the troubles of language and communication, mental retardation, and troubles of development. In addition, it is used to study and compare the profile of each group.
The study took place in the Resource Centre for Autism Haute Normandy in Rouen, France, (CRA). A population of 39 subjects in which we found that CARS is certainly useful as a screening and diagnostic tool. In addition, there are some items that are not considered to be discriminative between autism and both troubles of development and mental retardation. The vocation of CARS to evaluate the intensity of autistic disorders also provides differential guidance at least for language disorders. So it is necessary to combine and pass several tests to achieve the desired differential diagnosis in a specialized clinic.
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Key words: CARS, diagnosis, autism, mental retardation, development disorder, disorder speech and communication

Résumé
L’échelle d’évaluation d’Autisme Infantile (le CARS) est un instrument pour le criblage et le diagnostic. Notre présente étude a été exécutée pour évaluer la puissance distinctive du CARS au centre de diagnostic pour différencier l'autisme des autres troubles comme trouble du langage et de la communication, trouble du retard mental, et trouble du développement. Il sert aussi à étudier et comparer le profil de chaque groupe diagnostiqué. L'étude est faite au Centre des Ressources pour l'Autisme de Haute Normandie à Rouen, France, (CRA). Notre population était de 39 sujets. Nous résultats indiquent que le CARS est un outil performant de diagnostic. Néanmoins, il y a quelques items non distinctifs entre l'autisme et le trouble du développement et le retard mental. La vocation du CARS pour évaluer l’intensité des troubles autistiques donne aussi des indications différentielles, à tout le moins pour les troubles du langage. Donc il est nécessaire De combiner la passation de plusieurs tests pour parvenir au diagnostic différentiel souhaité dans un centre de consultation spécialisée.
Mot clé : CARS, diagnostic, autisme, retard mental, trouble du développement, trouble du langage et de la communication


Introduction

Autism is a complex developmental disability that typically appears during the first three years of life characterized by a triad of symptoms: 1- deficits in social reciprocal interaction, 2- deficits in verbal and non verbal communication, 3- stereotyped behaviours restricted to certain interest and limited imagination (DSMIV-TR, 2000; ICD-10,1993) . The prevalence of Autism Spectrum Disorders (ASD) has been reported to be 1.7 to 4 per 1000 and 3 to 7 per 1000 for all invading disorders of development (Fombonne, 2003). That represents approximately 10 times more cases from the studies published before 1990 (Baghdadli, 2005).
Possible reasons for this increase is the advance in the differential diagnosis and more specifically, the precise description of the symptoms, the increased public awareness of the existence, characteristics, symptomatology, and prevalence, the increased research on ADS… (Walker, 2008). There are several methods of assessing autism and related pervasive developmental disorders (PDDs) which have considerable attention in this time. Some of these are based on parent or caregiver report, such as the Autism Diagnostic Interview-Revised (ADI-R), and others rely on the clinician’s observation of the child, including the Autism Diagnostic Observation Schedule-Generic (ADOS-G) and the Childhood Autism Rating Scale (CARS). (Ventola et al, 2006; lord, 1991). These instruments may be developed for different purposes and at different times and, therefore, may or may not be based on the same conception of autism. (Saemundsen et al 2003). It is very important for clinical practice and for research on autism to study these diagnostic instruments.
The Childhood Autism Rating Scale (CARS) is the most widely used standardized instrument, specifically designed for screening and diagnosis of autism, it is used for children over 2 years to young teen, Published in 1980 (Schopler et al., 1980).
The CARS was originally correlated to the DSM-III and developed over a 15-year period, with more than 1,500 cases to incorporate five diagnostic systems: the Kanner (1943) criteria, the Creak (1964) points, the definition of autism by Rutter(1978), the National Society for Autistic Children, and that of DSM-III-R. Therefore the CARS can be criticized in that it no longer reflects the diagnostic criteria (e.g. DSM 4). (Perry et al, 2005).
From a historical point of view CARS was developed for administrative needs and for the research of program TEACCH (Treatment and Education of Autistic and related Communication handicapped Children) which was developed by Professor Eric Schopler and many of his colleagues at the University of North Carolina at Chapel Hill. It was the first state-supported, university-based program serving individuals with autism and their families.
The 15 items of CARS include Relationships with People, Imitation, Affect, Use of Body, Relation to Non-human Objects, Adaptation to Environmental Changes, Visual Responsiveness, Auditory Responsiveness, Near Receptor Responsiveness, Anxiety Reaction, Verbal Communication, Nonverbal Communication, Activity Level, Intellectual Functioning, and the clinician's general impression. It takes about 20-30 minutes to administer. Each item is rated a 1 to 4 points devised to 7 degrees (1-1.5-2-2.5-3-3.5-4), so the total score of CARS is between 15 and 60; which can de a useful measure for indicating the severity of autism. Autism is defined by a score of ≥ 30 points. The total scores from 30 to 36.5 points reflect mild to moderate autism, and scores over 36 define severe autism.
The reliability of CARS which has been presented in the manual was high; three types of evidence were used: a high internal consistency (0.94) and inter-fidelity correction of 0.71 which shows a perfect match between the two evaluations. In parallel, fidelity test-retest is good and indicates that CARS is stable over time even for over one year.
There are many studies concerning the CARS in different situations, for example, in clinical sitting, we find the study of Adrienne perry et al (2005) in Canada, which examined several questions pertaining to the CARS in five clinical groups of young children, in a sample of 274 preschool children aged 2-6 years, clinically diagnosed as falling in on of: Autism Disorder, PDD-NOS, MR, Delayed, and other. There was a moderate negative correlation of CARS scores and developmental level (both cognitive and adaptive), indicating significant shared variance. There were significant and sensible differences in mean CARS score for different diagnostic groups, including a substantial difference between the Autistic Disorder and PDD-NOS groups.
The study of Viviann Nordin et al (1998), was performed to assess the interrater reliability of a Swedish version of the CARS when used in a clinical setting, CARS was used for rating autistic behaviour by two investigations in 25 children. A variant of the weighted kappa statistic showed excellent agreement.
Other studies interested by the comparison between CARS and other instruments, as the study of Evald Saemundsen (2003), about the convergence and the discrepancy of Autism Diagnostic Interview-Revised (ADI-R) and CARS. The agreement between the two was investigated in the diagnostic assessment of 54 children aged 22-114 months referred for possible autism. CARS identified more cases of autism than ADI-R. Children classified as autistic according to both instruments had significantly lower IQ/DQ and more severe autistic symptomatology than those classified with the CARS only.
The study of E. Rellini, et al (2004) compared also CARS with (ABC) Autism Behavior Checklist, and verified their correspondence and conflict with a diagnosis made with DSM-4 criteria. The sample consisted of 65 children, aged 18 months to 11 years. They found agreement between DSM-4 and CARS. In addition, they show that ABC does not distinguish individuals with autistic disorders from other cases of developmental disorders as well as CARS.
But the study of Jennifer Stella et al in Florida (1999) interested by analyse of social and non-social factors in the CARS, for a sample of 90 children with diagnosis of either autism or PDDNOS, based on DSM-III-R diagnostic criteria.
Nevertheless, we always need to study more and examine all the aspects of CARS.
Our present study enters in the general problems of diagnosis of the autism. It was performed to analyze the CARS, when it is used in the psychological examinations in the diagnostic centres to differentiate the autistic children from the children with severe retardation of development, mental retardation and speech difficulty, and makes it possible to define different profiles of children according to their disorders.

The differential diagnosis

Autism and developmental disorder

Autism is one of five pervasive developmental disorders and it shares with other disorders of this category (Rett syndrome, trouble disintegration of the children, Asperger syndrome and pervasive developmental disorder not specified) the difficulties in three main areas: social functioning, communication and behavioral variability.
But we find other types of disorders of development in the CIM10 or DSM4, which is different from this category and that diagnosed some of our patients in our current study.
Autism and mental retardation

Mental retardation is a disorder often associated with autism and its considered as one of the differential diagnosis. It is important to note that about 80% of autism has mental retardation. The cognitive difficulties experienced by autistic children are mainly related to the capabilities of abstraction, conceptualization and symbolization. (Miljkouitch et al, 2003).
Only about a quarter of autism has an intellectual quotient in the normal range (IQ> 70). Two-thirds of them are located in range of moderate to severe debilitation (IQ <50).>
Autism and language disorders and communication

Speaking of language disorders and their distinction in relation to autism is not a simple task.
The mastery of language is absent from much (about half) of autism. For those who have a few bases, the language is generally not used for communication purposes (Miljkouitch et al, 2003).
In the same way, a child with an important disorder of language will also show retardation in quantitative terms of communication and possibly retardation in social interactions.
However, a child with a receptive or expressive language disorder will not present qualitative difficulties in social interaction and communication that can be observed in children with autism. The differentiation between quantitative and qualitative retardation may be difficult to achieve. Quantitative retardation means that a person has limited or special abilities compared to his chronological age or the standards expected. For example, a child with expressive language retardation will use fewer words in his vocabulary. The qualitative retardation signifies when person possessing an atypical behaviour compared to normal person. For example, a child with autism may not only have fewer vocabulary but also uses the words which he knows in an incorrect method grammatical compared to children with language retardation (ex. reversing pronouns, sentences) (Shriver et al, 1999. Petot, 2003).

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