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2 Diagnosis, Assessment, and Prevalence MULTIDISCIPLINARY PERSPECTIVES The diagnosis of autism and related autistic spectrum disorders in young children is often relatively straightforward but can, at times, be challenging (Lord, 1997). Complexities in diagnosis and evaluation relate to the range of syndrome expression in these conditions along various dimensions such as language abilities and associated mental handicap (Volkmar et al., 1997); differential diagnosis, particularly in children younger than 3 years (Lord and Schopler, 1989); concerns regarding label- ing (Hobbs, 1975) and diagnostic terminology within school systems; and lack of expertise in assessment and diagnosis among some educational professionals (Siegel et al., 1988). In general, the perspectives of various professionals are required as part of the diagnostic process. This may involve the efforts of special educators, general educators, psychologists, speech pathologists, occupa- tional and physical therapists, and physicians. The need for a multi- disciplinary or transdisciplinary perspective can create challenges for lo- cal educational authorities. Although the mandate of the local education authority (LEA) and state-funded developmental disability programs is to provide appropriate education, the services of non-LEA specialists are required for initial identification, diagnosis, and clinical services related to the presence of additional handicapping conditions. A LEA and state services may need to form relationships with individuals and centers with such expertise. Although various rating scales and checklists have been developed to aid in the process of assessment, these do not replace 23
24 EDUCATING CHILDREN WITH AUTISM the need for a thoughtful and comprehensive diagnostic assessment (dis- cussed below)âthis is particularly true for preschool children, for whom issues of diagnosis can be complicated. PREVALENCE OF AUTISM AND RELATED CONDITIONS Epidemiological studies of autism have important implications for both research and clinical service, for example, through helping to plan for the need for special services and selecting samples for research stud- ies. Fombonne (1999) has recently summarized the available research on this topic and systematically reviewed more than 20 studies conducted in ten countries. As he notes, although important details were sometimes lacking in the studies, the total population base included in the review was approximately 4 million children surveyed. Studies have typically employed a two-stage design, with an initial screening followed by more systematic assessment. Complexities in in- terpreting the available data include variations in approaches to diagno- sis of autism and differences in screening methods. In the studies sur- veyed, approximately 80 percent of individuals with autism also exhibited mental handicap (i.e., mental retardation). Studies have also consistently identified more boys with autism than girls (three to four boys for every girl). In addition, girls with autism are more likely than boys to also exhibit mental handicaps. The epidemiology of autism has recently become quite controversial. In the United States, increased demand for autism-specific services (Fombonne, 1999) has drawn attention to growing numbers of children with the educational categorization of autism. Large, systematic epide- miologic studies have reported increases in prevalence from the estimated rate of 2-5 per 10,000 in the 1970s to 6-9 per 10,000. Fombonne (1999) considers a rate of 7.5 per 10,000 to best reflect the result of studies con- ducted since 1987. Those studies also report a rate of 12.5 per 10,000 individuals for atypical autism/pervasive developmental disorders, pro- ducing an overall rate of about 20 cases per 10,000. Rates for Aspergerâs disorder, excluding individuals who also met criteria for autism, were low, at 1-2 per 10,000. Because the studies did not consider individuals with less-pronounced variants of autistic spectrum disorder, it is possible that the figures for atypical autism/pervasive developmental disorder and Aspergerâs disorder are underestimates. Two simple reasons explain the difference in current and historical rates: more complete diagnoses and a broader definition of autistic spec- trum disorders (Fombonne, 1999). However, there are a number of recent studies, most with small samples, and several reports from school sys- tems that found even higher rates of autism (Centers for Disease Control and Prevention, 2000; Arvidsson et al., 1997; Baird et al., 2000; Kadesjoe et
DIAGNOSIS, ASSESSMENT, AND PREVALENCE 25 al., 1999; California Department of Developmental Services, 2000). Stud- ies reporting much higher rates were from relatively small samples or from state surveys, in which an educational label of autism was associ- ated with provision of intensive services and thus highlight the need for further, well-designed investigations. For example, the Department of Educationâs Office of Special Education Programs (OSEP) could support a research study examining the prevalence and incidence of autism, using OSEP data gathered for school-age children since the autism category was recognized in 1991. This study could investigate in particular whether the dramatic increases in numbers of children served with autis- tic spectrum disorders are offset by commensurate decreases in categories in which children with autism might have previously been misclassified. SCREENING INSTRUMENTS The symptoms of autism are often measurable by 18 months of age (Charman et al., 1997; Cox et al., 1999; Lord, 1995; Stone et al., 1999; Baird et al., 2000). The main characteristics that differentiate autism from other developmental disorders in the 20-month to 36-month age range involve behavioral deficits in eye contact, orienting to oneâs name, joint attention behaviors (e.g., pointing, showing), pretend play, imitation, nonverbal communication, and language development (Charman et al., 1997; Cox et al., 1999; Lord, 1995; Stone et al., 1999). There are three published screen- ing instruments in the field that focus on children with autism: the Check- list for Autism in Toddlers (Baird et al., 2000), the Autism Screening Ques- tionnaire (Berument et al., 1999), and the Screening Test for Autism in Two Year Olds (Stone et al., 2000). The Checklist for Autism in Toddlers (CHAT) (Baron-Cohen et al., 1992; 1996) is designed to screen for autism only at 18 months of age. From both the initial study of siblings of children with autistic disorder and from a larger epidemiological study involving a population study of 16,000 18-month-old infants (excluding children with suspected develop- mental delays), virtually all the children failing the five item criterion on the CHAT administered twice (one month apart, the second time by an experienced clinician and including other sources of information) were found to have autistic disorder when diagnosed at 20 and 42 months (Baron-Cohen et al., 1992; Baron-Cohen et al., 1996; Charman et al., 1998; Cox et al., 1999). However, the CHAT was less sensitive to milder symp- toms of autism; children later diagnosed with other autistic spectrum disorders did not routinely fail the CHAT at 18 months. Follow-up of the cases at age 7 revealed that this instrument had a high specificity (98%) but relatively low sensitivity (38%) (Baird et al., 2000), suggesting that it is not appropriate for screening. The Autism Screening Questionnaire is a new 40-item screening scale
26 EDUCATING CHILDREN WITH AUTISM that has good discriminative validity between autistic spectrum and other disorders, including nonautistic mild or moderate mental retardation, in children age 4 years and older; it has not yet been tested with very young children. A score of 1 is given for an item if the abnormal behavior is present and a score of 0 if the behavior is absent. The cutoff for consider- ation of a diagnosis of autism is a score of 15 or higher. Further reliability studies and validation studies in younger children are ongoing. The re- cently published Screening Test for Autism in Two-Year Olds (Stone et al., 2000) is a direct observational scale; it showed good discrimination between children with autism and other developmental disorders in a small sample of two-year-old children. Several additional instruments are currently undergoing validation studies. The Australian Scale for Aspergerâs Syndrome (Garnett and Attwood, 1998) is a parent or teacher rating scale for high-functioning older children on the autistic spectrum who remain undetected at school- age. The Pervasive Developmental Disorders Screening Test-II (PDDST- II) is a clinically derived parent questionnaire designed in three formats: Stage 1 is aimed for use in the primary care setting, Stage 2 for use in developmental clinics, and Stage 3 for use in autism clinics. The Modified Checklist for Autism in Toddlers (M-CHAT) expands the CHAT into a 23- item checklist that a parent can fill out in about 10 minutes (Robins et al., 1999). Other approaches are being developed. ASSESSMENT Developmentally based assessments of cognitive, communicative, and other skills provide information important for both diagnosis and pro- gram planning for children with autism and related conditions. Careful documentation of a childâs unique strengths and weaknesses can have a major impact on the design of effective intervention programs and is particularly critical, because unusual developmental profiles are com- mon. Given the multiple areas of difficulty, the efforts of professionals from various disciplines are often needed (e.g., psychology, speech and language pathology, neurology, pediatrics, psychiatry, audiology, physi- cal and occupational therapy). The level of expertise required for effec- tive diagnosis and assessment may require the services of individuals, or a team of individuals, other than those usually available in a school set- ting (Sparrow, 1997). In some cases, psychological and communication assessments can be performed by existing school staff, depending on their training and competence in working with children with autism. How- ever, other services (e.g., genetic testing, drug therapy, management of seizures) are necessarily managed in the health care sector. Some chil- dren may fall between systems and therefore not be served well. Several principles underlie assessment of a young child with autism
DIAGNOSIS, ASSESSMENT, AND PREVALENCE 27 or autistic spectrum disorder (Sparrow, 1997): 1. Multiple areas of functioning must typically be assessed, including current intellectual and communicative skills, behavioral presentation, and functional adjustment. 2. A developmental perspective is critical. Given the strong associa- tion of mental retardation with autism, it is important to view results within the context of overall developmental level. 3. Variability of skills is typical, so it is important to identify a childâs specific profile of strengths and weaknesses rather than simply present an overall global score. Similarly, it is important not to generalize from an isolated or âsplinterâ skill to an overall impression of general level of ability, since such skills may grossly misrepresent a childâs more typical abilities. 4. Variability of behavior across settings is typical. Behavior of a child will vary depending on such aspects of the setting as novelty, de- gree of structure provided, and complexity of the environment; in this regard, observation of facilitating and detrimental environments is help- ful. 5. Functional adjustment must be assessed. Results of specific assess- ments obtained in more highly structured situations must be viewed in the broader context of a childâs daily and more typical levels of function- ing and response to real-life demands. The childâs adaptive behavior (i.e., capacities to translate skills into real world settings) is particularly impor- tant. 6. Social dysfunction is perhaps the most central defining feature of autism and related conditions, so it is critical that the effect of a childâs social disability on behavior be considered. 7. Behavioral difficulties also must be considered, since they affect both the childâs daily functioning and considerations for intervention. Various diagnostic instruments can be used to help structure and quantify clinical observations. Information can be obtained through ob- servation (e.g., the Autism Diagnostic Observation Scale, Lord et al., 2000) as well as the use of various diagnostic interviews and checklists, e.g., Autism Diagnostic Interview-Revised (Lord et al. 1994); Childhood Au- tism Rating Scale (Schopler et al., 1980); Autism Behavior Checklist (Krug et al., 1980); Aberrant Behavior Checklist (Aman and Singh, 1986). An adequate assessment will involve both direct observation and interviews of parents and teachers. The range of syndrome expression in autism and autistic spectrum disorders is quite broad and spans the entire range of IQ (Volkmar et al., 1997). A diagnosis of autism or autistic spectrum disorder can be made in a child with severe or profound mental retardation as well as in a child
28 EDUCATING CHILDREN WITH AUTISM who is intellectually gifted. In addition, individuals vary along a number of other dimensions, such as levels of communicative ability and degree of behavioral difficulties. As a result, in working with a child with an autistic spectrum disorder, considerable expertise is required of the vari- ous evaluators. Evaluators must consider the quality of the information obtained (both in terms of reliability and validity), the involvement of parents and teachers, the need for interdisciplinary collaboration, and the implications of results for intervention. Coordination of services, includ- ing specialized assessment services, is important, as is facilitating discus- sion between members of assessment and treatment teams and parents (Filipek et al., 1999; Volkmar et al., 1999). A range of components should be part of a comprehensive educa- tional evaluation of young children with autism. These include obtaining a thorough developmental and health history, a psychological assess- ment, a communicative assessment, medical evaluation, and, in some cases, additional consultation regarding aspects of motor, neuropsycho- logical, or other areas of functioning (Filipek et al., 1999; Volkmar et al., 1999). This information is important both to diagnosis and differential diagnosis and to the development of the individual educational interven- tion plan. The psychological assessment should establish the overall level of cognitive functioning as well as delineate a childâs profiles of strengths and weaknesses (Sparrow, 1997). This profile should include consider- ation of a childâs ability to remember, solve problems, and develop con- cepts. Other areas of focus in the psychological assessment include adap- tive functioning, motor and visual-motor skills, play, and social cognition. Children will usually need to be observed on several occasions during more and less structured periods. The choice of assessment instruments is a complex one and depends on the childâs level of verbal abilities, the ability to respond to complex instructions and social expectations, the ability to work rapidly, and the ability to cope with transitions in test activities (the latter often being a source of great difficulty in autism). Children with autism often do best when assessed with tests that require less social engagement and less verbal mediation. In addition to the formal quantitative information pro- vided, a comprehensive psychological assessment will also provide a con- siderable amount of important qualitative information (Sparrow, 1997). It is important that the psychologist be aware of the uses and limitations of standardized assessment procedures and the difficulties that children with autism often have in complying with verbal instructions and social rein- forcement. Operant techniques may be helpful in facilitating assessment. Difficulties in communication are a central feature of autism, and they interact in complex ways with social deficits and restricted patterns of behavior and interests in a given individual. Accurate assessment and
DIAGNOSIS, ASSESSMENT, AND PREVALENCE 29 understanding of levels of communicative functioning is critical for effec- tive program planning and intervention. Communication skills should be viewed in a broad context of an individualâs development (Lord and Paul, 1997; Prizant and Schuler, 1997); standardized tests constitute only one part of the assessment of communication abilities in younger children with autism and related conditions. The selection of appropriate assess- ment instruments, combined with a general understanding of autism, can provide important information for purposes of both diagnostic assess- ment and intervention. In addition to assessing expressive language, it is very important to obtain an accurate assessment of language comprehension. The presence of oral-motor speech difficulties should be noted. In children with au- tism, the range of communicative intents may be restricted in multiple respects (Wetherby et al., 1989). Delayed and immediate echolalia are both common in autism (Fay, 1973; Prizant and Duchan, 1981) and may have important functions. In addition, various studies have documented unusual aspects even of very early communication development in au- tism (Ricks and Wing, 1975; Tager-Flusberg et al., 1990). In assessing language and communication skills, parent interviews and checklists may be used, and specific assessment instruments for chil- dren with autistic spectrum disorders have been developed (Sparrow, 1997). For children under age 3, scores on standardized tests may be particularly affected by difficulties in assessment and by the need to rely on parent reports and checklists. For preverbal children, the speech- communication assessment should include observation of a childâs level of awareness of communication âbidsâ from others, the childâs sense of intentionality, the means used for attempting communication, and the quality and function of such means, sociability, and play behaviors. The evaluator should be particularly alert to the childâs capacity for symbolic behavior, because this has important implications for an intervention pro- gram (Sparrow, 1997). There are also several standardized instruments that provide useful information on the communication and language de- velopment of preverbal children with autism; these include the Commu- nication and Symbolic Behavior Scales, the Mullen Scales of Early Learn- ing, and the MacArthur Communicative Development Inventory. For children with some verbal ability, social and play behaviors are still im- portant in terms of clinical observation but various standardized instru- ments are available as well, particularly when a child exhibits multiword utterances. Areas to be assessed include receptive and expressive vo- cabulary, expressive language and comprehension, syntax, semantic rela- tions, morphology, pragmatics, articulation, and prosody. The choice of specific instruments for language-communication as- sessment will depend on the developmental levels and chronological age of the child. For higher functioning individuals with autism or Aspergerâs
30 EDUCATING CHILDREN WITH AUTISM syndrome, additional observations may address aspects of topic manage- ment and conversational ability, ability to deal with nonliteral language, and language flexibility. As with other aspects of assessment, an evalua- tor should be flexible and knowledgeable about the particular concerns related to assessment of children with autism. Motor abilities in autism may, at least in the first years of life, repre- sent an area of relative strength for a child, but as time goes on, the development of motor skills in both the gross and fine motor areas may be compromised, and motor problems are frequently seen in young chil- dren with autism. Evaluations by occupational and physical therapists are often needed to document areas of need and in the development of an intervention program (Jones and Prior, 1985; Hughes, 1996). Standard- ized tests of fine and gross motor development and a qualitative assess- ment of other aspects of sensory and motor development, performed by a professional in motor development, may be helpful in educational plan- ning. MEDICAL CONSIDERATIONS For very young children, there may be concerns about the child rec- ognized or first expressed in the context of well-child care. The education of physicians, nurses, and others regarding warning signs for autistic spectrum disorders is very important. After initial referral for assessment and diagnosis, consultations with other medical professionals may be indicated, depending on the context (Filipek et al., 1999; Volkmar et al., 1999), for example, to developmental and behavioral pediatricians, child psychiatrists, geneticists, and pediatric neurologists. When this consulta- tion is relevant to the educational program, reimbursement may appro- priately be made by the local education authority. The available literature has clearly documented that children with autism are at risk for developing seizure disorders throughout the devel- opmental period (Deykin and MacMahon, 1979; Volkmar and Nelson, 1990). Seizure disorders in autism are of various types and may some- times present in unusual ways. Although not routinely indicated, an electroencephalogram (EEG) and/or neurological consultation is indi- cated if any symptoms suggestive of seizures, such as staring spells, are present. The presence of a family history of developmental delay or unusual aspects of a childâs history or examination may suggest the need for genetic or other consultation. In some cases, autism may be associated with other conditionsânotably fragile X syndrome and tuberous sclero- sis (Dykens and Volkmar, 1997). A childâs hearing should be tested, but behavioral problems may sometimes complicate assessment. Definitive documentation of adequate
DIAGNOSIS, ASSESSMENT, AND PREVALENCE 31 hearing levels should then be obtained through other methods, such as auditory brainstem evoked responses (BSERs) (Klin, 1993). Certain fea- tures, such as the abrupt behavioral and developmental deterioration of a child who was previously developing normally, may suggest the impor- tance of extensive medical investigations (Volkmar et al., 1999). In some cases, the use of psychotropic medications may be indicated for young children (see Chapter 10). Although not curative, such medica- tions may help to reduce levels of associated maladaptive behaviors and help children profit from educational programming. The use of such agents requires careful consideration of potential benefits and risks and the active involvement of parents and school staff (see Volkmar et al., 1999 for a review). IMPLICATIONS FOR INTERVENTION Many aspects of the procedures, curricula, and educational programs relevant to other children are readily applicable to children with autism and related conditions. As for all children, an intervention program must be individualized and tailored to the specific needs, strengths, and weak- nesses of the individual child. In addition, children with autistic spec- trum disorders often present special challenges for intervention. From the time of Kannerâs (1943) definition of autism, social deficits have been consistently identified as an, if not the, essential feature of the condition. Social interaction requires careful attention to multiple, shift- ing strands of information; an ability to perceive the thoughts, feelings, and intentions of others; and coping with novel situations on a regular basis. In children with autistic spectrum disorders, social difficulties per- sist over time, although the nature of the social difficulties may change with age and intervention (Siegel et al., 1990). These social difficulties, as reflected in relationships with teachers and particularly in relationships with peers, are different from those seen in all other developmental disor- ders and present special difficulties for programming. For a child with an autistic spectrum disorder to be able to be included in mainstream set- tings, the child must be able to manage social experiences. This requires careful consideration on the part of school staff. While children with an autistic spectrum disorder can be served within many school environ- ments, even for more cognitively able individuals this can be a challenge. The characteristic difficulties in social interaction require special teacher training and support beyond knowledge concerning general developmen- tal delays or other learning disabilities.