doi:10.1111/j.1440-1754.2007.01232.x

ORIGINAL ARTICLE

Diagnostic labelling of autism spectrum disorders in NSW Katrina Williams,1,2 Marshall Tuck,3 Megan Helmer,1 Lawrence Bartak,4 Craig Mellis1,2 and Jennifer K Peat1,2 on behalf of the Autism Spectrum Disorder Steering Group 1 Clinical Epidemiology Unit, 3Department of Psychological Medicine, The Children’s Hospital at Westmead, Westmead, 2University of Sydney, Sydney, New South Wales, and 4Faculty of Education, Monash University, Melbourne, Victoria, Australia

Aim: To describe the use of diagnostic labels by clinicians for children with autism spectrum disorders (ASD) and calculate the label-specific and overall agreement between diagnostic labels and Diagnostic and Statistical Manual of Mental Disorders – Fourth Edition (DSM-IV) diagnoses provided by the same clinician. Methods: State-wide active surveillance was used to ascertain children newly recognised with one or more DSM-IV criteria for autistic disorder aged 0–15 years (incident cases) in New South Wales (NSW) between July 1999 and December 2000. Clinicians were asked to supply a diagnostic label and then complete DSM-IV criteria for each child reported. Results: Questionnaires with diagnostic label and DSM-IV criteria were returned for 348 children. The agreement between labels used and diagnosis based on DSM-IV classification system was the highest for autism (97%) and lower for labels of Asperger disorder, pervasive developmental disorder – not otherwise specified or atypical autism (27%). Kappa overall agreement was 0.31. Level of agreement between label and DSM-IV diagnosis was similar for questionnaires completed by multidisciplinary teams, psychiatrists, paediatricians and psychologists working as part of a team. Conclusion: A lack of agreement between the diagnostic labelling used by clinicians and diagnosis based on DSM-IV criteria indicates a lack of consistency in diagnostic communication that is necessary to provide best clinical care, appropriate services and relevant information to parents and carers. Key words:

Asperger syndrome; autistic disorder; pervasive developmental disorder; diagnosis.

Although autism was first described in the 1940s,1 the classification of autism and related disorders, such as Asperger disorder, are still disputed. For example, an overlap in diagnosis of autistic disorder and Asperger disorder has been described,2 with some children satisfying the criteria for both disorders, leading many authors to question whether autism and Asperger disor-

Key Points 1 The term ASD is widely used but currently has no associated diagnostic classification. 2 Agreement between labels used by clinicians and DSM-IV diagnoses is low, except for the labels autism or Autistic Disorder. 3 Consistency in the use of diagnostic labels is important for communicating with parents, professionals and service providers. Correspondence: Dr Katrina Williams, Sydney Children’s Community Health Centre, Cnr Barker and Avoca Streets, Randwick, NSW 2031, Australia. Fax: +61 9382 8188; email: [email protected]. nsw.gov.au Katrina Williams, Community Paediatrician, Sydney Children’s Hospital; Marshal Tuck, Public Health Officer trainee, NSW Department of Health; Craig Mellis, Associate Dean, Sydney University; Lawrence Bartak, Retired; Jennifer K Peat, Epidemiology and statistical consultant; Megan Helmer, Data manager for Eli Lilly. Accepted for publication 26 June 2007.

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der can be differentiated.3–5 Further, Diagnostic and Statistical Manual of Mental Disorders – Fourth Edition (DSM-IV) 6 and International Classification of Diseases – Tenth Revision (ICD107) do not define diagnostic criteria for pervasive developmental disorder – not otherwise specified (PDD-NOS)8,9 and a reconceptualisation of autism diagnosis based on developmental trajectory has been suggested10,11 but not yet developed. Recently, the term autism spectrum disorders (ASD) has been developed12–14 because children with abnormalities of communication, behaviour and/or social interaction of the type seen in autism have been identified who do not fulfil all of the diagnostic criteria for autism. However, there is no currently accepted diagnostic classification system that uses the term ASD. As such it has been suggested that it should only be used as the collective term for a group of defined disorders.15 Current practice therefore requires that ASD are diagnosed using either DSM-IV6 or ICD-107 classification systems. These versions have superseded all previous DSM and ICD classifications. DSM-IV diagnostic categories considered by most clinicians and researchers as ASD are autistic disorder, Asperger disorder and PDD-NOS. The ICD-10 diagnostic categories considered to be ASD are childhood autism, Asperger syndrome, atypical autism, other pervasive developmental disorder (PDD) and PDD-unspecified. In addition, disorders not listed as PDD in ICD-10 or DSM-IV have been linked to autism and are considered by some to be part of the autism spectrum. These disorders include deficits in attention, motor control and perception,16

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other disorders of empathy (including anorexia nervosa)17 and semantic-pragmatic language disorder.18 In this paper we describe diagnostic labels used for children reported with one or more criteria for DSM-IV diagnosis of autistic disorder in New South Wales (NSW) between July 1999 and December 2000 and calculate the label-specific and overall agreement between diagnostic labels used by clinicians and DSM-IV diagnoses.

Materials and Methods Active surveillance with monthly mail-out to over 466 professionals was completed between July 1999 and December 2000. Active surveillance was modelled on the Australian Paediatric Surveillance Unit and other international surveillance units.19,20 Detailed information about recruitment and participation of the mailing list has been published previously.12 Clinicians were asked to complete questionnaires. In brief, the clinicians who completed questionnaires included paediatricians (general, developmental, community, geneticist, neurologists and adolescent physicians), child and adolescent psychiatrists, clinicians representing multidisciplinary developmental teams, psychologists working for community service teams, speech and language therapists and psychologists working in private. To achieve ascertainment of children with problems across the autism spectrum, a definition was established that identified eligible children as those who met one or more criteria for autistic disorder (299.00) outlined in DSM-IV.6 Children needed to have been newly recognised with these problems by professionals in the last month, commencing July 1999.

Diagnosis of autism in NSW

To allocate DSM-IV diagnoses clinical diagnostic criteria for autistic disorder and Asperger disorder were used (Box 1) and DSM-IV diagnostic criteria applied. To fulfil a diagnosis of autistic disorder a total of six clinical features needed to be identified with at least two social interaction features and at least one communication problem and one behavioural problem. For Asperger disorder, communication clinical features are not included in the clinical features list. There needed to be qualitative impairment in social interactions, as manifested by at least two social interaction clinical features and restricted repetitive and stereotyped patterns of behaviour, interests and activities as manifested by at least one clinical feature (Box 1). To identify children who would satisfy both autistic disorder and Asperger disorder diagnostic criteria, information provided by clinicians was reviewed to assess whether there was no clinically significant general delay in language and no clinically significant delay in cognitive development. As no criteria for PDD-NOS are specified in DSM-IV, to satisfy this diagnosis cases were required to have been assigned two social interaction criteria, at least one communication or behavioural criterion and a total of four DSM-IV criteria. These criteria require more autistic criteria than cut-offs suggested by some authors.21 Once a child was reported, checking to ensure that the report was not a duplicate of a previous report was completed and questionnaires were sent to the appropriate clinician. The questionnaire sent to clinicians asked for the ‘current working diagnosis or problem list’ for the child. On the next page the clinician was asked to tick boxes to indicate the presence or absence of the 12 clinical criteria used to make a DSM-IV diagnosis of autistic disorder.

Box 1 DSM-IV clinical features for autistic disorder and Asperger disorder A. Communication Qualitative impairment in communication as manifested by any of the following: 1 Delay in, or total lack of, the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime) 2 In individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others 3 Stereotyped and repetitive use of language or idiosyncratic language 4 Lack of varied, spontaneous make-believe play or social imitative play appropriate to developmental level B. Behaviour Restricted, repetitive and/or stereotyped patterns of behaviour, interests, and/or activities, as manifested by any of the following: 5 Encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or in focus 6 Apparently inflexible adherence to specific, non-functional routines and rituals 7 Stereotyped and repetitive motor mannerisms (e.g. hand or finger flapping or twisting, or complex whole-body movements 8 Persistent preoccupation with parts of objects C. Social interaction Qualitative impairment of social interaction, as manifested by any of the following: 9 A marked impairment in the use of multiple non-verbal behaviours such as eye-to-eye gaze, facial expression, body postures, and gestures to regulate social interaction 10 Failure to develop peer relationships appropriate to developmental level 11 A lack of spontaneous seeking to share enjoyment, interests, or achievements with other people (e.g. by a lack of showing, bringing, or pointing out objects of interest) 12 Lack of social or emotional reciprocity

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622 eligible children 139 Incomplete information about diagnosis

126 De-identified reports sent 9 no autistic Label given

348 Diagnostic label and DSM-IV criteria provided 107 Autism spectrum disorder 107 Autism, autistic disorder, classical autism, childhood autism

7 Pervasive developmental disorder

71 Asperger syndrome, PDD-NOS or atypical autism

56 Autistic features, SPLD, language disorder/delay

Fig. 1 Information available and diagnostic label given for eligible children. DSM-IV, Diagnostic and Statistical Manual of Mental Disorders – Fourth Edition (DSM-IV); PDD-NOS, pervasive developmental disorder – not otherwise specified; SPLD, semantic pragmatic language disorder.

Statistical analysis Data were stored in a Microsoft access database. Per cent agreement was calculated between each diagnostic label and DSM-IV diagnosis. SPSS version 11.5 (SPSS Inc, Chicago, IL, USA) was used to calculate Kappa statistics of agreement to provide a measure of overall agreement that takes into account agreement that may have occurred by chance alone. The range of possible values for Kappa is from -1 to 1 but values usually fall between 0 and 1, with 0 indicating agreement no better than expected by chance or as if raters had ‘guessed’ every rating.22 We also calculated overall agreement adjusted for overlap between Asperger syndrome and autistic disorder diagnoses.

Results A total of 622 eligible children were identified.12 As shown in Figure 1, some clinicians elected to send de-identified reports instead of questionnaires (126, 20%), or did not provide complete information about diagnosis (139, 22%). Nine clinicians provided complete information but only provided a label that was not an autistic label, for example, developmental delay, attention deficit hyperactivity disorder and learning difficulties. Only reports with both clinician-completed DSM-IV and current working diagnosis or problem list and an autistic label could be directly compared (348, 56%). Table 1 shows information for children in which DSM-IV diagnosis and diagnostic label were able to be compared and those that were not, for the differences for diagnostic label proportions (when provided), age of the sample and clinicians providing information. 110

Of the 348 children for whom the reporting clinician provided a diagnostic label and completed the DSM-IV criteria, 15 children were assigned two autism labels by reporting clinicians; PDD/ASD (six), ASD/semantic pragmatic language disorder (five), autism/ASD (two), Asperger/semantic pragmatic language disorder (one), ASD/atypical autism (one). For analysis, if another label was given as well as the label ASD or PDD, the alternative label was used (Fig. 1). Table 2 shows the variation between diagnostic labelling used by clinicians and the DSM-IV criteria-based diagnosis. Most children labelled as ASD or PDD fulfilled criteria for autistic disorder (92%). For statistical analysis of agreement, the labels given by clinicians were condensed to equivalent DSM-IV diagnostic groups (Table 3). The most commonly used label, ASD, is a term that includes many of the listed PDDs in DSM-IV and could therefore not be condensed to a DSM-IV diagnostic group. Similarly the label PDD could not be compared with one DSM-IV diagnostic group. As a result, analysis was limited to comparison of diagnostic label and DSM-IV criteria-based diagnosis for 234 children. Per cent agreement was the highest between clinicians using the label ‘autism or Autistic disorder’ and DSM-IV criteria diagnosis of autistic disorder (97%). Per cent agreement between labelling as Asperger syndrome, PDD or atypical autism (27%) and labelling as another ASD (30%), with DSM-IV classification for these diagnoses, were lower. If agreement between DSM-IV criteria-based diagnosis and label is considered, 56% (104/185) who fulfilled autistic disorder criteria were labelled ‘autism or autistic disorder’. As such, 81 (44%) children were given a label other than ‘autism or autistic disorder’ when sufficient DSM-IV criteria were reported to satisfy that diagnosis. Kappa measurement of overall agreement between clinician labels and DSM-IV criteria-based diagnosis was 0.31. Table 4 shows the variation in diagnostic labelling for the professional groups completing most questionnaires. As shown, per cent agreement ranged from 94% to 100% for those labelled as autism, from 22% to 45% for those labelled as Asperger disorder or PDD-NOS and from 13% to 50% for those given other labels. Kappa measurement of agreement between DSM-IV criteria and diagnostic label ranged from 0.18 to 0.43 for different professional groups and practice types. Analysis of level of agreement by age group was possible for children aged 0–4 and children aged 5–9, with Kappa equal to 0.40 and 0.18, respectively. Of the 56 children labelled as Asperger disorder, 43 fulfilled the criteria for autistic disorder (Table 2). Of these, 14 were said by clinicians to have developmental delay or intellectual impairment or ‘delay in the, or total lack of, development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime)’. As such, these children would not fulfil diagnostic criteria for DSM-IV Asperger disorder. The remaining 29 children were excluded from the analysis to assess the impact of the overlap of these two disorders on agreement between labelling and DSM-IV diagnosis. Kappa measure of agreement between clinical labels and DSM-IV was higher overall (Kappa = 0.42) and for professional groups (Kappa ranged from 0.30 to 0.52) (Table 4).

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Table 1

Diagnosis of autism in NSW

Clinical descriptors of compared and not compared eligible cases reported to the study

Diagnostic labels n (%)

Autism Asperger syndrome/PDD-NOS/atypical autism ASD/PDD SPLD/LDD/autistic features

Age of children mean (95% CI) Proportion of children seen by type of reporting clinician n (%)

Paediatrician Multidisciplinary team Psychologist working with a team Psychiatrist

Sample that could be compared. n (%)

Sample not able to be compared. n (%)

107 (31%) 70 (20%) 112 (32%) 56 (16%) 4.42 (4.18,4.66) 195 (56%) 49 (14%) 64 (18%) 26 (7%)

29 (12%) 76 (32%) 56 (24%) 51 (22%) 6.43 (6.02,6.84) 97 (35%) 52 (19%) 7 (3%) 22 (8%)

ASD, autism spectrum disorders; CI, confidence interval; LDD, language disorder or delay; PDD, pervasive developmental disorder; PDD-NOS, pervasive developmental disorder – not otherwise specified; SPLD, semantic pragmatic language disorder.

Table 2 Comparison of diagnostic label and DSM-IV criteria-based diagnosis DSM-IV diagnosis

Diagnostic label

AD

PDD/As perger

Another ASD

ASD Autism† Asperger syndrome Atypical autism Pervasive developmental disorder PDD-NOS Autistic features Language disorder/delay Semantic pragmatic language disorder Total

100 104 43 1 5 6 20 5 6

5 2 11 2 2 6 4 3 1

2 1 2 0 0 0 3 9 5

107 107 56 3 7 12 27 17 12

290

36

22

348

Total

†Autism was used for the diagnostic labels Autistic Disorder, Childhood Autism, autism and classical autism. AD, Autistic Disorder; ASD, autism spectrum disorders; Diagnostic and Statistical Manual of Mental Disorders – Fourth Edition (DSM-IV); PDD, pervasive developmental disorder; PDD-NOS, pervasive developmental disorder – not otherwise specified.

Discussion In NSW between 1999 and 2000 the term ASD was widely used as a diagnostic label by clinicians. For specific diagnostic labels like classical autism, autistic disorder and autism, agreement between label and DSM-IV diagnoses based on diagnostic criteria provided by the same clinician was high. However, for other autism spectrum labels, like Asperger disorder, atypical autism and PDD-NOS, agreement with equivalent DSM-IV diagnoses based on diagnostic criteria provided by the same clinician was low. Low agreement was also seen between other labels used by clinicians who reported children to this study, like semantic pragmatic language disorder, language disorder/delay and autistic features, and DSM-IV diagnoses based on diagnostic criteria

they provided. Overall agreement was higher when children who satisfied both autistic disorder and Asperger disorder diagnostic classification were excluded, but this overlap did not account for all the lack of agreement found. The concept of autism as a spectrum of disorders has been useful to identify children with similar patterns of problems with social interaction, communication and behaviour.12,13 It is therefore not surprising that it is widely but variably used in Queensland.23 However, the lack of any current diagnostic criteria associated with the term ASD means that the interpretation of its meaning in terms of a child’s problem profile is difficult. In this study most children labelled as an ASD fulfilled DSM-IV diagnostic criteria for autistic disorder. If each of these children had been instead described as autistic disorder, there would be a generally accepted understanding of the minimal level of dysfunction that they were experiencing. Highest per cent agreement for autism and lower agreement for other diagnoses such as Asperger disorder, PDD-NOS and atypical autism, are consistent with international studies. In one study, using ‘DSM-IV autistic disorder field trial’ data, clinicians felt more confident in clinical diagnoses of autism than in diagnoses of PDD-NOS and non-PDD disorders.21 In another study using DSM-IV field trial data, 46% of clinician diagnoses of PDD-NOS or atypical autism satisfied at least one diagnostic classification system diagnosis of autism.24 The majority of children given labels other than ‘autism’ fulfilled DSM-IV criteria for autistic disorder (Table 3). This could occur as a result of clinicians preferring to use ‘less severe’ labels to describe children with autistic disorder. Clinicians reporting to this study knew that it was not linked to service provision. However, this practice is the opposite of that described in a recent study in which clinicians reported they would provide an autism diagnosis on a service-providers form when their diagnostic specification had not been met.25 Alternatively the use of ‘less severe’ labels could occur because the application of DSM-IV criteria is not always straightforward, especially in the context of determining developmentally appropriate behaviour. There is also little guidance about the severity or pervasiveness required for clinical criteria. As such clinicians may identify that DSM-IV clinical criteria are satisfied but use a

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Table 3 Numbers of children for diagnostic labels used by clinicians compared with DSM-IV criteria-based diagnosis, with per cent of agreement between these shown for each diagnostic label category DSM-IV diagnosis Diagnostic label

AD

PDD/Asperger

Another ASD

Total

Autism† Asperger syndrome/PDD-NOS/atypical autism Autistic features/language disorder/delay or semantic pragmatic language disorder Total

104 (97%) 50 31

2 19 (27%) 8

1 2 17 (30%)

107 71 56

185

29

20

234

†Autism was used for the diagnostic labels autistic disorder, childhood autism, autism and classical autism. AD, Autistic Disorder; ASD, autism spectrum disorders; Diagnostic and Statistical Manual of Mental Disorders – Fourth Edition (DSM-IV); PDD, pervasive developmental disorder; PDD-NOS, pervasive developmental disorder – not otherwise specified.

Table 4 Numbers of children for diagnostic label and DSM-IV diagnosis for different clinicians and clinical settings with per cent agreement between these shown for each diagnostic label category DSM-IV diagnosis

Information source

Diagnostic label

AD

PDD/ Asperger

Another ASD

Kappa overall

Kappa†

Multidisciplinary

Autism Asperger syndrome/PDD-NOS/atypical autism SPLD/LDD/autistic features Autism Asperger syndrome/PDD-NOS/atypical autism SPLD/LDD/autistic features Autism Asperger syndrome/PDD-NOS/atypical autism SPLD/LDD/autistic features Autism Asperger syndrome/PDD-NOS/atypical autism SPLD/LDD/autistic features

15 (94%) 6 3 60 (97%) 21 15 24 (100%) 9 6 3 (100%) 11 1

1 5 (45%) 3 1 6 (22%) 4 0 3 (23%) 1 0 5 (29%) 0

0 0 4 (40%) 1 0 10 (35%) 0 1 1 (13%) 0 1 1 (50%)

0.43

0.52

0.33

0.45

0.25

0.32

0.18

0.30

Paediatrician

Psychologist working with a team Psychiatrist

†For sample excluding 29 children who fulfilled both autistic disorder and Asperger syndrome criteria. AD, Autistic Disorder; ASD, autism spectrum disorders; LDD, language disorder or delay; PDD, pervasive developmental disorder; PDD-NOS, pervasive developmental disorder – not otherwise specified; SPLD, semantic pragmatic language disorder.

different diagnostic label to convey their overall clinical impression to takes into account the severity and pervasiveness of the constellation of clinical features and the child’s developmental age. Unfortunately not all children who were eligible from statewide active surveillance in NSW were able to be included in this analysis, as a result of multiple approaches to data collection used by the study. It is therefore not possible to be certain that these findings would apply to all children ascertained in NSW in 1999–2000. However, the children not able to be included were more likely to have been given a label other than ‘autism’ (agreement lower) and were older (agreement lower). As a result, the sample included in this study is likely to have a higher level of agreement between label provided and DSMIV diagnosis than the sample that could not be included. In 112

addition, because the same clinician provided the label and the DSM-IV data, this study reports level of agreement using a method that would bias results towards a high level of agreement.22 It is therefore unlikely that this study reports a biased overestimation of the lack of agreement between the labels clinicians use and DSM-IV diagnostic criteria. A lack of agreement between diagnostic labels used and accepted classification system-based diagnoses raises two important issues. The first is the likely lack of consistency in the use of diagnostic labels. This is supported by findings in Queensland which describes considerable variation regarding use of terminology and diagnostic constructs.23 This has implications for best clinical care in terms of communicating level of need with other professionals, service providers, parents and carers and for accessing services, which are often label-dependent. The second

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is the bigger issue of diagnostic validity for non-autism diagnoses, including the problem described by Baird regarding the overlap of diagnosis for Asperger disorder and autistic disorder with DSM-IV.2 Lack of clarity of appropriate diagnostic labelling, even when currently accepted diagnostic criteria are used, creates problems for clinicians. Current best practice for diagnosis is the use of existing classification systems and widespread uptake of this practice will improve diagnostic consistency. This in turn will increase consistency of diagnostic label usage so that families, clinicians, other service providers and service funders can communicate effectively about the needs of children with ASD. Further work is needed, and is ongoing internationally, to improve the validity of diagnostic classification systems so that diagnostic allocation will assist decision-making about most appropriate treatments and prognosis predictions.

Acknowledgements The authors would like to thank all those on the mailing list who returned cards or completed questionnaires, the Autism Spectrum Disorder Steering Group, and Greta Ridley and Danielle Wheeler (The Childern’s Hospital at Westmead, NSW) for editorial comment. We also thank the organisations who supported this study (DET, DoCS, Autism Association of NSW, The Children’s Hospital at Westmead, Sydney University) and the Apex Foundation for Research into Intellectual Disability, Children’s Hospital Fund of the Children’s Hospital at Westmead and Financial Markets Foundation for Children for funding. The research has been undertaken with assistance from the NSW Department of Ageing, Disability and Home Care. However, the information and views contained in this study do not necessarily, or at all, reflect the views or information held by the NSW Government, the Minister for Ageing, Minister for Disability Services, or the Department.

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