Autistic spectrum disorder: diagnostic difficulties

Autistic spectrum disorder: diagnostic difficulties

Prostaglandins, Leukotrienes and Essential FattyAcids (2000) 63(1/2), 33^36 & 2000 Harcourt Publishers Ltd doi:10.1054/plef.2000.0188, available onlin...

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Prostaglandins, Leukotrienes and Essential FattyAcids (2000) 63(1/2), 33^36 & 2000 Harcourt Publishers Ltd doi:10.1054/plef.2000.0188, available online at http://www.idealibrary.com on

Autistic spectrum disorder: diagnostic difficulties G. S. Jones Woodlands Hospital, Cults, Aberdeen, UK

Summary Recognition of the autistic spectrum disorders is becoming more widespread amongst basic scientists, clinicians, and the generalpopulation.The term doesnot implyanythingabout pathologyoraetiology, althoughit hasproved to be a useful concept clinically. From Kanner's classical autism the concept has widened in scope to include milder and more subtle impairments.From a clinicalperspective, there are manyalternative diagnosesin an individualwith autistic-like symptoms, and thorough investigation is necessary to exclude these. & 2000 Harcourt Publishers Ltd

INTRODUCTION Autistic spectrum disorder describes a group of related conditions classified under the pervasive developmental disorders. They are characterized by specific language difficulties, impairments of social communication, and specific cognitive impairments. No single cause has been identified, but the condition affects a minimum of 4 per 10,000 births, with milder symptoms being present in as much as 17 per 10,000. The condition predominately affects boys in a ratio of approximately 4 to 1, although this sex ratio is not as great in less severe forms. Subsequent research has brought the autistic spectrum disorders to the fore, in research where work on associations and aetiology continues to expand, in clinical work where psychologist, psychiatrists and paediatricians are increasingly aware of the possibility of this diagnosis and its implications for management, and in families and people with the diagnosis who have an interest in service provision. With this heightened interest it is worth reviewing the concept of the disorder and the potential pitfalls it creates. These can be considered under three separate headings:

Received 28 February 2000 Accepted 17 March 2000 Correspondence to: G. S. Jones MRCPsych, Specialist Registrar in Psychiatry of Learning Disability,Woodlands Hospital, Craigton Road, Cults, Aberdeen AB15 9PR, UK.Tel.: +44 (0) 1224 663131; Fax: +44 (0) 1224 404018; E-mail: [email protected]

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semantic problems; classification problems; and diagnostic problems.

SEMANTIC PROBLEMS The term autism was initially used by Kanner to describe the aloofness and separateness from the world exhibited by this group of children. He derived the term from an earlier one by Bleuler, who had used it to describe the way in which patients with schizophrenia related to their environment. In this way, it developed connotations of being related to schizophrenia, but it was not until 1971 that the two conditions were clearly discriminated.1 Since then the concept of an autistic spectrum has been developed to take into account the association seen between the severe classical autism, Asperger's syndrome, and less severe impairments. In their original papers, Kanner and Asperger described a set of symptoms observed in a group of children. It is important to realise that they described a syndrome, rather than a disease, and that this is what continues to be described in the International Classification of Diseases.2 Rather than being the clinical manifestation of a single pathological process, the autistic spectrum disorders may well be the final common pathway of several, perhaps quite different, pathologies. This would be in keeping with recent associations of autistic spectrum disorder with conditions as diverse as birth trauma, genetic diseases, and food intolerance. Therefore, accounts of phenomena relating to `autism' might describe what are

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in fact quite different pathological processes that may merely have common symptoms. An analogy might be drawn with chest pain, which might have musculoskeletal, cardiac, respiratory, or gastrointestinal origins. Given the relative lack of information about aetiology, it is clear that presently there is no gold standard test for autism and presently the diagnosis is one that can only be made on purely clinical grounds. CLASSIFICATION PROBLEMS The terms `autism', `autistic spectrum disorder', and `Asperger's syndrome' have acquired different meanings at different times and places. The terms have been used interchangeably with other terms such as `autistic psychopathy of childhood', 'childhood schizophrenia', and 'schizoid disorder of childhood'. Consensus has arrived through the two main classification systems, the International Classification of Diseases2 and the Diagnostic and Statistical Manual of the American Psychiatric Association,3 however, even these two authorities differ in their exact classification of the syndromes. Other authors have devised their own operational definitions, and this is particularly evident when the subject is Asperger's syndrome, with descriptions from Wing,4 and Gillberg and Gillberg,5 amongst others. Some authors have regarded schizoid personality disorder and Asperger's syndrome as being interchangeable, or different variants of the same underlying disorder,6,7 whilst others have differentiated the two on clinical ground.8 Thus, whilst the term `autistic spectrum disorder' has come into common usage, there is still some confusion as to exactly what the term refers to. Diagnostic criteria need to be clarified to identify the problems being identified. At present there is confusion as to the exact meaning and boundaries of the concept, and the descriptions already suggested remain open to different interpretations.7 DIAGNOSTIC PROBLEMS The assessment of a child who has abnormal communication, altered or abnormal responses to stimuli, and obsessive features is involved and complex. The diagnosis of autistic spectrum disorder is not one to make lightly, and requires a considerable investment in time interviewing parents, carers, teachers, and with the child himself. Although diagnosis is often viewed as the province of paediatricians or psychiatrist, parallel assessment from occupational therapists, speech and language therapists, clinical psychologists and other professionals is essential. There are a number of rating scales available to the clinician to help in the diagnosis. The `Checklist for Autism in Toddlers'9 is a useful screening tool intended

for primary care. The `Autism Diagnostic Interview'10 and the `Handicaps, Behaviours and Skills Questionnaire'11 are lengthy comprehensive tools requiring a trained interviewer and can take several hours to complete. They are less practical for the busy clinician in the outpatient department. Other conditions may mimic the symptoms of autistic spectrum disorder; the converse is also often true. Deafness or partial hearing loss is a common problem and can result in symptoms similar to autism. Lack of responsiveness to social cues, inattentiveness, and social isolation are all possible features. It is important that all children in which autism is suspected are given an audiological assessment. Psychosocial deprivation, similarly, can produce symptoms of withdrawal and abnormal verbal and non-verbal communication. Abnormal environments, physical and emotional abuse can produce abnormal behaviours and communication skills in otherwise normal children. Assessing the child in his own environment can give vital clues as to the underlying problem, as does collaborative histories from teachers and other carers who are often well informed about social backgrounds. Generalized learning disability is a common co-morbid disorder in patients with autistic spectrum disorder; and many patients with a learning disability have autistic traits although may not have sufficient to warrant the diagnosis of autism proper. The relationship is not an inevitable one and there is a significant proportion of individuals who have IQs in the normal range. It is unclear how much autism can cause learning disability, how much learning disability can cause autistic features, and how much underlying pathological processes that cause learning disability can also be responsible for autism.12 Behavioural syndromes associated with medical causes of learning disability can often produce a picture similar to autism. Fragile-X syndrome produces a characteristic picture of shy, embarrassed social behaviour with avoidance of gaze that was long thought to be autistic in nature, although an association is now thought to be spurious. Autism has historically been linked to schizophrenia. Although a number of studies have shown an increased incidence of schizophrenic symptoms, these have suffered from small sample numbers. Larger studies, for example by Kanner13 and Ghaziudden et al.14 have failed to show an excess of schizophrenia in autistic spectrum disorder populations. Frank delusions and hallucinations are relatively rare in autism, with an incidence similar to that of the general population15 but the so called `negative' schizophrenic symptoms of passivity, withdrawal, and poverty of thought may appear similar to those of autism. However, if diagnostic errors have been made in the past, it is more likely that schizophrenia

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Autistic spectrum disorder: diagnostic difficulties 35

has been diagnosed instead of autism, rather than vice versa. The relationship between schizoid personality disorder and autism, more particularly Asperger's syndrome, is a complex one. Many authors (for example, Nagy and Szatmari,16 Wolff,6 and Wing7 ) view the conditions as related, if not interchangeable. The difficulty may be one of semantics or of degree. Patients described as having Asperger's syndrome often have developmental abnormalities, whereas those described as having schizoid personality disorder do not. Patients with Asperger's have been shown to have an excess of affective disorder and have an excess of affective disorder in family members, whereas this relationship does not appear to hold true for patients with schizoid personality disorder.8,17 The relationship between the two conditions remains obscure, however, and, as is the case with schizophrenia, it is likely that schizoid personality disorder has been diagnosed in place of autistic spectrum disorder, rather than vice versa. Obsessional and compulsive symptoms are common in autistic spectrum disorders. They may take the form of obsessional interests, thoughts, collecting, use of language; or compulsive acts and rituals. However, these are but one feature of the larger clinical picture. Patients with obsessive±compulsive disorder (OCD) may demonstrate similar symptoms but lack the specific language and social relationship impairments. OCD also tends to respond to pharmacological or behavioural interventions and in the longer term has a better prognosis. There tends not to be the autistic picture of normal general development then a decline in functional ability. The clinical picture in OCD may show relapse and remission, whereas in the autistic spectrum disorder the clinical picture is more or less constant and unremitting. The family history also give some clues to diagnosis. Disorders such as schizophrenia often show marked familial tendencies but there is no reported excess of schizophrenia in families of individuals with autistic spectrum disorder. Autistic traits, communication difficulties, and learning disability have been described in family members of autistic individuals, for example by Gillberg.18 The diagnosis of autistic spectrum disorder is a difficult one and requires a full clinical, psychological, and speech and language assessment. Where aetiology remains unclear, further laboratory investigations are recommended. These include audiometry; electroencephalogram (EEG); metabolic assessment including quantitative amino acids, urine organic acids, thyroid function, lactate pyruvate and carnitine levels; and karyotyping, including testing for fragile X. Neuroimaging is generally only indicated if there are suggestions of focal lesion, for example clinical evidence of tuberose sclerosis.19 & 2000 Harcourt Publishers Ltd

Autistic spectrum disorder presents a greater diagnostic challenge in general the older the patient is at first presentation. Adults, for example, may have more subtle language, cognitive, and social impairments than others who have been diagnosed earlier in life. The formerly lower profile of this disorder has in the past undoubtedly led to individuals being diagnosed incorrectly, leading to suboptimal management, oversight of key areas in communication in social skills, and perhaps inappropriate prescribing. Whilst the tendency to underdiagnose the condition may be changing, we must be careful by clarifying our ideas about the disorder that it does not become overdiagnosed.

REFERENCES 1. Kolvin I. Studies in childhood psychoses: I. Diagnostic criteria and classification. B J Psych 1971; 118: 381±384. 2. World Health Organisation. The ICD-10 Classification of mental and behavioural disorders. Geneva: World Health Organisation, 1992. 3. American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 4th ed. Washington DC: American Psychiatric Association, 1994. 4. Wing L. Asperger's syndrome: a clinical account. Psychol Med 1981; 11: 115±129. 5. Gillberg C., Gillberg C. Asperger's syndrome: some epidemiological considerations: a research note. J Child Psychol Psychiat 1989; 30: 631±638. 6. Wolff S. Loners: the life path of unusual children. London: Routledge, 1995. 7. Wing L. The autistic spectrum. Lancet 1997; 350: 1791±1796. 8. Tantam D. Lifelong eccentricity and social isolation. II: Asperger's syndrome or schizoid personality disorder? B J Psych 1988; 153: 783±791. 9. Baron-Cohen S., Allen J., Gillberg C. Can autism be detected at 18 months? The needle, the haystack, and the CHAT. B J Psych 1992; 161: 839±843. 10. Le Couteur A., Rutter M., Lord C., et al. Autism diagnostic interview: a standardised investigator instrument. J Autism Dev Disord 1989; 19: 363±387. 11. Wing L. Wing schedule of handicaps, behaviours and skills (HBS). In: Rapin I., ed. Preschool children with inadequate communication. Clinics in Developmental Medicine No. 139. London: MacKeith Press, 1996. 12. Berney P. Autism Ð an evolving concept. B J Psych 2000; 176: 20±25. 13. Kanner L. Childhood psychosis initial studies and new insights. New York: Winston/Wiley 1973. 14. Ghaziudden M., Tsai L. Y., Ghaziudden N. Co-morbidity of autistic disorder in children and adolescents. Eur J Child Adol Psychiat 1992; 1: 209±213. 15. Howlin P. Autism: preparing for adulthood. London: Routledge 1997: 217±220. 16. Nagy J. Szatmari P. A chart review of schizotypal personality disorders in children. J Autism Dev Dis 1986; 16: 351±367. 17. Nordin V., Gillberg C. The long term course of autistic disorders: update on follow-up studies. Acta Psych Scand 1998; 97: 999±1087.

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18. Gillberg C. Six family studies. In: Frith U., ed. Autism and Asperger's Syndrome. Cambridge: Cambridge University Press, 1991: 122±146.

19. Geschwind D., Cummings J. L., Hollander E., et al. Autism screening and diagnostic evaluation: CAN consensus statement. CNS Spectrums 1998; 3: 3, 40±49.

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