Assessment Instruments for Asperger Syndrome

Measurement Issues: Asperger Syndrome

Assessment Instruments for

Asperger Syndrome

Patricia Howlin

This review describes the current situation with regard to diagnostic

instruments for Asperger syndrome. The paucity of such instruments, and

the lack of adequate standardisation data amongst the few that do exist,

represent a serious omission for both clinicians and researchers. The major

problem limiting the development of effective diagnostic or screening

instruments is the confusion inherent in ICD-10 and DSM-1V systems in

differentiating autism from Asperger syndrome. In the absence of clear and

clinically satisfactory diagnostic criteria, efforts to develop valid

assessment instruments may be attempting to put the horse before the

cart!

Keywords: Asperger syndrome; assessment instruments; diagnosis

Background

In contrast to Kanner’s (1943) descriptions of autism,

which rapidly gained wide recognition, the initial accounts

of ‘Asperger syndrome’ (Asperger, 1944) remained in

relative obscurity for almost 40 years. Being written in

German just at the end of the Second World War clearly

did not help and it was not until 1981, when Lorna Wing

published a detailed account of 34 further cases, that

interest in the condition began to re-emerge. However,

even then there was significant opposition to the use of this

label as separate from autism (Schopler, 1985). Although

such scepticism has not entirely disappeared (Schopler,

Mesibov, & Kunce, 1998), Asperger syndrome was finally

included in both DSM-IV and ICD-10 classifications in

the 1990s (World Health Organisation, 1990; American

Psychiatric Association, 1994).

Perhaps because of the delay between initial description

and final inclusion in formal diagnostic systems, the

diagnosis of Asperger syndrome has tended to give rise to

far more confusion amongst clinicians than the diagnosis

of autism. This may be due to a number of different

reasons.

1. Current criteria for Asperger syndrome have moved

away somewhat from Asperger’s own descriptions. In-

deed, many of the cases whom he described would not

actually fulfil current DSM}ICD" specifications (Miller &

" Throughout the remainder of the text the initials DSM and

ICD are used to refer to DSM-IV and ICD-10.

Ozonoff, 1997). Recent clinical accounts have remained

closer to Asperger’s initial version but are not necessarily

identical to this (see Table 1).

2. Although current ICD}DSM criteria make clear the

overlap with autism (see Tables 2 & 3), the distinguishing

features are not always clear. Thus, although early

language delays are cited as one of the main differential

criteria, there is no precise definition of what a ‘clinically

significant ’ delay entails. Does this apply, for example, to

children who, despite having begun to use words by 2 and

phrases by 3 years of age, as stipulated in ICD}DSM, are

still clearly well behind in their language development

when formally assessed? Moreover, it is not uncommon

for some children, who fail to use single words by the

specified age of 2 years, then to make rapid progress and

be using good phrase speech by 3 years. There is no

guidance on how delays in receptive language should be

defined, and other linguistic impairments, notably the

abnormalities in reciprocity and pragmatics that are

typical of individuals with a diagnosis of Asperger

syndrome, are simply not mentioned at all. Similar

confusion arises over acceptable IQ levels. Although ICD

criteria note : ‘Self-help skills (and) adaptive behaviour

during the first 3 years should be at a level consistent with

normal intellectual development’, no developmental or

IQ cut-offs are specified.

3. Considerable problems arise from the fact that DSM

and ICD criteria indicate that, for a diagnosis of autism:

‘ the clinical picture is not attributable to other varieties of

Patricia Howlin

Department of

Psychology, St

George’s Hospital

Medical School,

Cranmer Terrace,

London SW17 ORE

Child Psychology & Psychiatry Review Volume 5, No. 3, 2000120


Table 1. Differing criteria for Asperger syndrome

AuthorDate(Nsubjects)

Asperger,1944(< 200)

Wing, 1981(34)

Gillberg &Gillberg,1989 (23)

Szatmari etal., 1989(28)

Tantam,1991 (85)

ICD-10,1992

DSM-IV,1994

Exclusionof autism

Yes

No

No

Yes

No

?

Yes

Clumsy

+

+

+

+

+

Usually

May bepresent

All-absorbinginterests

+

+

+

+

+

+ (or rigidbehaviourspatterns)

+ (or rigidbehaviourspatterns)

Abnormalcommuni-cation

+

+

+

+

+

Autisticsocialimpairment

+

+

+

+

+

+

+

Rarely present

May bepresent

May bepresent

May bepresent

–

–

Cognitivedelays

–

May bepresent

May bepresent

May bepresent

–

–

Languagedelay

+ = Characteristic deemed necessary for diagnosis; – = Characteristic deemed to exclude diagnosis(Blank = no specific mention)

pervasive developmental disorder ’ (i.e., the diagnosis of

autism should not be given if the case meets criteria for

Asperger syndrome). The same caveat also applies to

Asperger syndrome– i.e., this diagnosis should not be

given if the case meets criteria for autism. What to do,

therefore, with cases who meet the criteria for social and

repetitive abnormalities required for both autism and

Asperger syndrome, are of normal IQ, and who had no

early language delays, but nevertheless show difficulties in

maintaining or initiating conversations, have repetitive

and}or stereotyped speech, and have never played

imaginatively (as per criteria for autism)? DSM-IV adopts

a hierarchical stance, in that if criteria for autism are met

then that diagnosis should take precedence. However,

Manjiviona and Prior (1999) note that if this rule were to

be strictly followed, the number of cases diagnosed as

having Asperger syndrome would be minimal. For this

reason, other researchers, such as Kim et al. (2000),

have adopted the opposite strategy, in that if criteria for

autism are fulfilled, but IQ and early language devel-

opment are in the normal range, the diagnosis of Asperger

syndrome takes precedence.

4. Research studies seeking to determine whether there is

a fundamental difference between Asperger syndrome and

autism, have, if anything, tended to confuse the picture

even further. This is partly because they have not

consistently used the same differentiating criteria (with

subgroups sometimes being distinguished on the basis of

motor clumsiness, sometimes on current linguistic or

cognitive functioning, but only rarely according to strict

DSM guidelines ; Manjiviona & Prior, 1999) and partly

because of the different research paradigms used. Overall,

the number of studies suggesting that Asperger and high

functioning autism groups differ on cognitive, social,

motor or neuropsychological tasks probably equals those

indicating no difference (Klin & Volkmar, 1997; Howlin,

1998; Schopler et al., 1998). For example, Klin and

Volkmar (1997) suggest that ‘AS differs from HFA (high

functioning autism) in that the outset is more positive

…social and communication deficits are less severe

…motor mannerisms are usually absent and circum-

scribed interests more conspicuous’. They also note that

motor clumsiness and a positive genetic history are more

common in Asperger syndrome. However, in fact, there is

no consistent evidence that children with Asperger syn-

drome are (relative to IQ) less socially impaired; they are

not necessarily clumsier (Manjiviona & Prior, 1995) ; the

genetic background is not always stronger (Bolton et al.,

1994) and outcome can sometimes be very poor (Howlin,

1998).

5. Clinicians, understandably confused by all this con-

flicting evidence, have tended to adopt their own working

definitions, with variable degrees of consistency. Some

have used the diagnosis for individuals who, although

clearly meeting criteria for autism when younger, later

show little sign of linguistic or cognitive impairment. In

Child Psychology & Psychiatry Review Volume 5, No. 3, 2000 121


Table 2. ICD-10 criteria for autism

A. Abnormal or impaired development is evident before the age of 3 years in at least one of the followingareas:

(1) receptive or expressive language as used in social communication;(2) the development of selective social attachments or of reciprocal social interaction;(3) function or symbolic play.

B. A total of at least six symptoms from (1), (2), and (3) must be present, with at least two from eachof (2) and (3):

(1) Qualitative abnormalities in reciprocal social interaction are manifest in at least two of the followingareas:(a) failure adequately to use eye-to-eye gaze, facial expression, body posture, and gesture to

regulate social interaction:(b) failure to develop (in a manner appropriate to mental age, and despite ample opportunities)

peer relationships that involve a mutual sharing of interests, activities, and emotions;(c) lack of socio-emotional reciprocity as shown by an impaired or deviant response to other

people’s emotions: or lack of modulation of behaviour according to social context; or a weakintegration of social, emotional, and communicative behaviours;

(d) lack of spontaneous seeking to share enjoyment, interests, or achievements with other people(e.g., lack of showing, bringing, or pointing out to other people objects of interest to theindividual).

(2) Qualitative abnormalities in communcation are manifest in at least one of the following areas:(a) a delay in, or total lack of, development of spoken language that is not accompanied by an

attempt to compensate through the use of gesture or mime as an alternative mode of communi-cation (often preceded by a lack of communicative babbling);

(b) relative failure to initiate or sustain conversational interchange (at whatever level of languageskills is present), in which there is reciprocal responsiveness to the communcations of the otherperson;

(c) stereotyped and repetitive use of language or idiosyncratic use of words or phrases;(d) lack of varied spontaneous make-believe or (when young) social imitative play.

(3) Restricted, repetitive, and stereotyped patterns of behaviour, and activities are manifest in at leastone of the following areas:(a) an encompassing preoccupation with one or more stereotyped, restricted patterns of interest

that are abnormal in content or focus; or one or more interests that are abnormal in theirintensity and circumscribed nature though not in their content or focus;

(b) apparently compulsive adherence to specific, non-functional routines or rituals;(c) stereotyped and repetitive motor mannerisms that involve either hand or finger flapping or

twisting, or complex whole body movements;(d) preoccupations with part-objects or non-functional elements of play material (such as their

odour, the feel of their surface, or the noise or vibration that they generate).

C. The clinical picture is not attributable to the other varieties of pervasive developmental disorders;specific developmental disorder of receptive language with secondary socio-emotional problems;reactive attachment disorder or disinhibited attachment disorder; mental retardation with someassociated emotional or behavioural disorder; schizophrenia of unusually early onset; and Rett’ssyndrome.

other cases, the label has been used as an alternative for

obsessional or social disorders, atypical autism, PDD-

NOS, non-verbal learning disability (Klin et al., 1995) or

‘schizoid personality disorders ’ (Wolff & McGuire, 1995).

Given the persisting confusion as to what Asperger

syndrome actually is, it is hardly surprising that very few

diagnostic instruments have been designed specifically to

identify it. The following account, therefore, summarises

the criteria used in the most widely cited clinical accounts,

briefly reviews instruments for autism that might be

utilised for diagnosing Asperger syndrome, and finally

covers the few scales specifically developed for Asperger

syndrome.

Principal clinical accounts

Asperger’s (1944) initial accounts of the syndrome are

extremely lengthy and detailed (see translation by Frith,

1991). Because of their complexity, they cannot easily be

used as clinical guidelines but the following are the main

features noted:

E Impairments in non-verbal communication (affecting

vocal intonation and facial expression).

E Idiosyncrasies in verbal communication (poor conver-

sational skills ; long-winded, literal and pedantic

speech; lack of reciprocity).

E Poor social adaptation and special interests (egocentric

preoccupation with particular topics, often precluding



A. There is no clinically significant general delay in spoken or receptive language or development.Diagnosis requires that single words should have developed by 2 years of age or earlier and thatcommunicative phrases be used by 3 years of age or earlier. Self-help skills, adaptive behaviour, andcuriosity about the environment during the first 3 years should be at a level consistent with normalintellectual development. However, motor milestones may be somewhat delayed and motor clumsinessis usual (although not a necessary diagnostic feature). Isolated special skills, often related to abnormalpreoccupations, are common, but are not required for diagnosis.

B. There are qualitative abnormalities in reciprocal social interaction (criteria as for autism; see Table2 above).

C. The individual exhibits an unusually intense, circumscribed interest or restricted, repetitive, andstereotyped patterns of behaviour, interests and activities (criteria as for autism, see Table 2; however,it would be less usual for these to include either motor mannerisms or preoccupations with part-objects or non-functional elements of play materials).

D. The disorder is not attributable to the other varieties of pervasive developmental disorder; simpleschizophrenia; schizotypal disorder; obsessive-compulsive disorder; anankastic personality disorder;reactive and disinhibited attachment disorders of childhood, respectively.

Table 3. ICD-10 criteria for Asperger’s syndrome

acquisition of practical self-help skills ; social difficulties

often resulting in severe teasing}bullying).

E ‘Intellectualisation of affect ’ (poor empathy, tendency

to intellectualise feelings}emotions).

E Clumsiness and poor body awareness (odd gait and poor

motor coordination).

E Conduct problems (aggression, non-compliance, nega-

tivism).

E Problems present in first 2–3 years of life (although

sometimes not noted until later).

E Significant family history (cases almost exclusively

male).

Wing (1981)

Wing’s (1981) list of the principal symptoms is based on

her summary of Asperger’s writings, and her own clinical

experience.

E Speech : may be some early delays, but these are not

particularly severe. Grammar and vocabulary are good

but speech is often pedantic, literal and stereotyped.

Lack of reciprocity; no drive to communicate ; does not

draw others’ attention to things of interest. Impaired

imaginative ability.

E Non-verbal communication : limited and}or inappro-

priate facial}vocal expression; poor understanding}misinterpretation of others’ gestures and expressions.

E Social interaction : poverty of reciprocal social inter-

action: inability to understand and use the rules

(especially unwritten rules) governing social behaviour;

naı$ve and}or inappropriate behaviour; lack of empa-

thy. Often bullied and teased by others.

E Repetitive activities and resistance to change : e.g.,

spinning objects ; unhappiness away from familiar

environment}routines ; intense attachment to particu-

lar possessions. Play may be repetitive and stereotyped

despite some imaginative content.

E Skills and interests : intense interests in one or two

subjects (e.g., bus timetables, the royal family) to the

exclusion of all else. Excellent rote memory and able to

remember all the relevant facts about their particular

interest, but often without any real understanding of

these.

E Motor co-ordination : clumsy and ill co-ordinated; odd

posture and gait ; poor at group games}sports ; fine

motor skills may be poor.

E Some indication of genetic causes, but pre}peri}post

natal neurological conditions also noted.

Although this account is based closely on Asperger’s own

writings, Wing disagrees with Asperger on two particular

points. She notes that language is often more im-

poverished, and sometimes more delayed, than in

Asperger’s accounts. Thought processes are not original

and creative, as Asperger suggested, but narrow, pedantic

and logical.

Gillberg and Gillberg (1989)

The characteristics Gillberg and Gillberg (1989) describe

are very similar to those of Wing, but the minimum

number of symptoms necessary to fulfil diagnostic criteria

is specified.

E Impairments in reciprocal social interaction (at least two

of the following) :

a) inability to interact with peers

b) lack of desire to interact with peers

c) lack of appreciation of social cues

d) socially and emotionally inappropriate behaviour

E All absorbing narrow interest (at least one of the

following) :

a) exclusion of other activities

b) repetitive adherence

c) more rote than meaning



E Imposition of routines and interests (at least one of the

following) :

a) on self, in aspects of life

b) on others

E Speech and language problems (at least three of the

following) :

a) delayed development

b) superficially perfect language

c) formal pedantic language

d) odd prosody, peculiar voice characteristics

e) impairment of comprehension including mis-

interpretations of literal}implied meanings

E Non-verbal communication problems (at least one of the

following) :

a) limited use of gestures

b) clumsy}gauche body language

b) limited facial expression

c) inappropriate expression

d) peculiar, stiff, gaze

E Motor clumsiness

Poor performance on neuro-developmental exam-

ination.

Gillberg and Gillberg (1989) also note a strong genetic

history and the presence of neurological impairments.

Tantam (1991)

Tantam’s (1991) account differentiates between diagnostic

criteria in adulthood and in childhood.

In adulthood

E Lack of non-verbal expressiveness, associated with

either

a) idiosyncratic facial expressions, gestures, voice

prosody, or posture and}or

b) an inability to recognise socially important cues.

E Unusual ‘special ’ interests that are narrow and private.

The special interests may be idiosyncratic and}or

pursued obsessively. Often involve collecting objects or

memorising facts.

E Difficulty in behaving according to socially accepted

conventions, particularly when these are normally im-

plicit.

E Pragmatic abnormalities of speech

E Lack of close peer relationships, often but not always as

a result of social advances being rebuffed by peer.

E Impression of clumsiness

In childhood

Symptoms as above, or symptoms of autism. If a

childhood history is unavailable, the symptoms cannot be

attributed to psychosis occurring in adulthood.

Szatmari, Bremner and Nagy (1989)

Szatmari, Bremner and Nagy’s (1989) suggested criteria

are based on items that were found to differentiate between

individuals with Asperger syndrome and non-Asperger

controls.

E Solitary – two of:

a) No close friends

b) Avoids others

c) No interest in making friends

d) A loner

E Impaired social interaction –one of:

a) Approaches others only to have own needs met

b) A clumsy social approach

c) One-sided responses to peers

d) Difficulty sensing feelings of others

e) Detached from feelings of others

E Impaired non-verbal communication –one of:

a) Limited facial expression

b) Unable to read emotion from facial expression of

child

c) Unable to give message with eyes

d) Does not look at others

e) Does not use hands to express oneself

f) Gestures are large and clumsy

g) Comes too close to others

E Odd speech – two of:

a) Abnormalities in inflection

b) Talks too much

c) Talks too little

d) Lack of cohesion to conversation

e) Idiosyncratic use of words

f) Repetitive speech patterns

E Does not meet DSM-IV criteria for autistic disorder

Diagnostic and screening instruments

Non-Asperger syndrome specific

Although, as noted above, there are few diagnostic

instruments specifically for Asperger syndrome there are

many for autism more generally. These include check lists

and rating scales such as the Rimland Diagnostic Form

for Behavior Disturbed Children (version E-2; Rimland,

1971) ; the Behavior Rating Scale for Autistic and Atypical

Children (BRIAC; Ruttenberg et al., 1966) ; Gilliam

Autism Rating Scale (Gilliam, 1995) ; the Childhood

Autism Rating Scale (CARS; Schopler, Reichler, &

Renner, 1988) and the Autism Behavior Checklist (ABC;

Krug, Arick, & Almond, 1980). Of these, the latter two

have been most widely evaluated and appear to have

acceptable levels of reliability and validity (Lord, 1997).

There are also much more detailed observational or

interview based assessments such as the Autism Diag-

nostic Interview-Revised (ADI-R; Lord, Rutter, & Le

Couteur, 1994) and the Autism Diagnostic Observation

Schedule-Generic (ADOS-G; Lord et al., 1999). More

recently, too, the Autism Screening Questionnaire

(Berument et al., 1999), which is based on questions

selected from the ADI-R, has been developed. This has

good discriminative validity with respect to the separation

of Pervasive Developmental Disorder (PDD) from non-

PDD diagnoses at all IQ levels but is weaker at differen-

tiating between autism and other varieties of PDD (such

as Asperger syndrome and atypical autism).



Lord (1997) discusses the merits and drawbacks of many

of these instruments. Whilst she notes that none actually

meet all the American Psychological Association

standards of reliability and validity (APA, 1985) the more

widely used of these instruments, such as the ADI or ABC,

do provide information on validity and reliability. Data

on specificity and sensitivity, as well as discriminant

validity and factor structure, are also increasingly avail-

able (e.g., Tanguay, Robertson, & Derrick, 1998;

Wadden, Bryson, & Rodger, 1991).

Both the ADI and the ABC have been used to identify

individuals with Asperger syndrome and}or high

functioning autism, although not to distinguish between

the two. Yirmaya, Sigman and Freeman (1994) examined

their value in identifying high functioning autism in a

group of 18 children (full scale IQ 75–136), all of whom

had been diagnosed as meeting DSM-IV criteria for

autism by experienced clinicians. On the ABC, when

retrospective ratings were used, based on the children’s

behaviour between 3 and 5 years (current behaviour

ratings were not sensitive to diagnosis), 15 individuals

scored above cut-off and the remaining 3 fell within the

borderline range. However, although the ABC may reach

acceptable levels of sensitivity within the higher

functioning group, its specificity within this subgroup has

not been evaluated. Problems may also arise because of

significant differences between parent and teacher ratings

(Szatmari et al., 1994).

Fifteen out of the 18 children were also assessed on the

original version of the ADI (Le Couteur et al., 1989).

Twelve obtained an unequivocal diagnosis of autism. The

three who were not identified all had IQs above 120 (two

of these also had borderline scores on the ABC). Yirmaya

et al. (1994) suggest that although the original ADI may

lack sensitivity in diagnosing very intelligent autistic

individuals, the ADI-R (Lord et al., 1994), with its

expanded social algorithm and less stringent criteria for

stereotyped}repetitive behaviour patterns, may prove to

be more useful. Given that, in order to meet ICD}DSM

criteria for Asperger syndrome, individuals must meet the

same criteria for abnormalities in social interaction and

stereotyped patterns of behaviours}interests as for autism,

the ADI-R clearly offers the potential for identifying cases

of Asperger syndrome. The author’s personal experience

of using the ADI-R with a large number of more able

(often adult) patients indicates that clients with the typical

clinical characteristics of Asperger syndrome almost

always score above the threshold for impairments in social

interaction and stereotyped behaviours}interests. The

problem is that, although they are not reported to have

had early language delays, they still meet criteria for

autism on the ADI communication algorithm because of

their many other abnormalities in reciprocal communi-

cation. This brings us back once more to the inherent

confusion in ICD}DSM systems in attempting to dis-

tinguish between autism and Asperger syndrome.

The Diagnostic Interview of Social and

Communication Disorders (DISCO; Leekam et

al., 2000)

This is a semi-structured interview for parents and carers,

adapted from the Handicaps Behaviour and Skills sched-

ule (HBS, Wing & Gould, 1978). Data on specificity and

sensitivity are not yet available but assessments of

reliability and validity are currently in progress. The aim is

to provide users with algorithms that can differentiate

between subgroups within the autistic spectrum, but no

feature has been identified that could distinguish between

Asperger syndrome and other forms of autism (Leekam et

al., 2000). Indeed, on the basis of research findings and

clinical experience, the authors suggest ‘ there is little point

in pursuing the question of the differentiation of autism

and Asperger syndrome’.

Assessments for Asperger syndrome

Among the few assessment instruments designed

specifically to identify Asperger syndrome fewer still are

able to demonstrate that they meet the basic psychometric

requirements of :

E Reliability (inter-rater, test-retest or internal consist-

ency)

E Validity (construct, content or criterion-related)

E Sensitivity : the proportion of cases correctly identified

(true positives)

E Specificity : the proportionof non-cases correctly identi-

fied (true negatives).

The Australian Scale for Asperger syndrome

(Garnett & Attwood, 1995; Attwood, 1998)

This is a 24-item scale that uses a 7-point rating system.

The areas covered include: Social and emotional abilities

(understanding how to play, peer interactions, under-

standing of social conventions}other people’s feelings and

ideas, empathy, display of emotion etc.) ; Communication

(literal understanding, unusual eye-contact}tone of voice,

lack of reciprocal conversation, pedantry etc) ; Cognitive

skills (memory, reading, imaginative play) ; Specific

interests (preoccupations, dislike of change, routines and

rituals) ; Movement skills (odd gait, poor co-ordination),

and Other characteristics (fears and phobias, sensitivity to

pain, motor mannerisms etc). It is meant to be used as a

screening instrument on which to base decisions about the

need for a full diagnostic assessment. However, scoring

criteria are unclear in that it is suggested simply that ‘If the

answer is yes to the majority of questions…and the rating

was between 2 and 6 (i.e., conspicuously above the normal

range)…Asperger’s syndrome…is a possibility and a

referral for a diagnostic assessment is warranted.’



There are no data on reliability, validity, specificity or

sensitivity, nor any analysis of factor structure.

Pervasive Developmental Disorders

Questionnaire (PDD-Q; Baron-Cohen, 1996)

This is an 18-item parental questionnaire, still in the

piloting stage, which covers various aspects of children’s

social and language competence at the age of 5 years. It

includes nine questions specifically designed to identify

behaviours characteristic of Asperger syndrome or Per-

vasive Developmental Disorders. These relate to spon-

taneous chat, greeting, offering comfort, sharing interests,

preoccupying interests, successful play with others, upset

at changes in routine, particular routines}insistence on

sameness, and idiosyncratic interests. Initial pilot studies

indicated that 37 out of 40 children (92.5%) already

diagnosed as having Asperger syndrome failed more than

five of the above items. This cut-off has been selected for

use in further research studies, related to the author’s

continuing validation of the CHAT (Checklist for Autism

in Toddlers ; Baron-Cohen et al., 1996). However, it is

unclear whether the questionnaire will be capable of

distinguishing between individuals with Asperger syn-

drome and other autism disorders, or will serve as a more

general screening instrument to identify high functioning

individuals within the spectrum.

Autism Spectrum Quotient (AQ; Baron-Cohen

et al., in press)

This is a 50-item self-assessment questionnaire, designed

for use by high functioning individuals within the autistic

spectrum. There are 5 groups of 10 questions, focusing on

social skill, attention to detail, attention switching, com-

munication, and imagination. Each item is rated on a 4-

point scale. The scores of 58 adults diagnosed as having

Asperger syndrome or high functioning autism were

compared with those of 174 randomly selected controls,

840 Cambridge undergraduates and 16 winners of the UK

Mathematics Olympiad. Eighty percent of the Asperger

group scored above the critical score of 32 (mean¯ 35.8),

whilst only 2% of the randomly selected and under-

graduate controls did so (mean¯ 16.4). Test-retest and

inter-rater (self vs. informant) reliability were assessed in

a small subgroup. Correlations were high (r¯ .7) and

internal consistency was good (ranging from .63 to .77).

The AQ still requires further research but these initial

findings indicate that it is sensitive to differences between

high functioning individuals with autistic disorders and

normal controls. Again, however, there is no indication

that it will be able to differentiate between Asperger

syndrome and high functioning autism. The authors also

stress that it should not be used as a diagnostic tool, but

suggest that it fills the gap for a brief assessment

instrument for more able individuals with autism and may

be useful for identifying cases for whom a full diagnostic

assessment is merited.

Screening questionnaire for Asperger

syndrome and other high functioning autism

spectrum disorders in school age children

(ASSQ; Ehlers, Gillberg, & Wing, 1999)

This is a 27-item checklist for completion by lay

informants. The items covered are derived from the

clinical criteria of Gillberg and Gillberg (1989) listed

above, and are rated on a 3-point scale. Data were based

on a mixed group of 110 6–17-year-olds referred to a state-

wide neuropsychiatric clinic. Twenty-one had a diagnosis

of autistic spectrum disorder, 58 of attention deficit}behavioural disorders, and 31 of learning disability. An

additional sample of 34 boys with Asperger syndrome

aged 6–16 years was used as a comparison with the rest of

the autistic spectrum group.

Reliability and validity

For the scale as a whole, test-retest correlations over 2

weeks were high (r" .90) for both teachers and parents,

and inter-rater correlations between teachers and parents

were significant (r¯ .66). The authors also note that there

was ‘a clear correspondence between total score and

clinical diagnoses (p¯ .0001) ’ and that autism spectrum

disorders could be significantly differentiated from the

other groups of disorder.However, no further information

is provided. When compared with other instruments

designed to measure non-specific behavioural problems

(i.e., divergent validity) correlations were .77 and .75; with

the Rutter Scales (A and B; Rutter, 1967; Rutter, Tizard,

& Whitmore, 1970) and .70 with the Connors scale

(Connors, 1990). These are higher than those recom-

mended by Streiner (1993) who suggests that a correlation

between .30 and .70 indicates that instruments are

complementary, rather than equivalent.

Sensitivity and specificity

As the authors point out, there is always a trade off here

because sensitivity can only be increased at the expense of

specificity. They used a ROC analysis (Receiver Operating

Characteristic, Goodman, 1994; Fletcher, Fletcher, &

Wagner, 1988) which plots the false positive rate against

the false negative rate for each score. Cut-off scores of 19

for parent ratings (which correctly identified 82% of

cases) and 22 for teacher ratings (‘hit rate ’ 65%) are

suggested as optimal for identifying likely autistic spec-

trum disorders, whilst minimising the rate of false

positives. Higher cut-off scores (of 22 and 24), while

further decreasing the rate of false positives, resulted in

failure to identify up to 57% of autistic spectrum cases.

The ASSQ is the only screening instrument specifically

designed for high functioning individuals within the

autistic spectrum for which detailed reliability and validity

data are available. However, as the authors themselves

point out, the standardisation sample is very small and the

scale does not differentiate cases of Asperger syndrome

from those with high functioning autism.

The Asperger syndrome diagnostic interview

Gillberg and his colleagues have recently also developed a



longer diagnostic interview based on the ASSQ. This

comprises 20 questions and cases need to meet criteria for

abnormality in six areas: reciprocal social interaction;

restricted interest patterns ; routines and rituals ; speech

and language; non-verbal communication, and motor

clumsiness. Although data on only 13 cases with Asperger

syndrome}autism are reported (Gillberg et al., in press),

the initial findings suggest that the instrument has ac-

ceptable levels of reliability and validity. However, it is

not designed to distinguish between people with Asperger

syndrome and other high functioning individuals within

the autistic spectrum. Indeed, like Leekam et al. (2000)

the authors question both the feasibility and practical

value of such a goal. They also note that the instrument

is to be used to aid clinical diagnosis and that ‘It should

not be used as the only and final instrument’.

Conclusions

Despite the fact that recent figures from the National

Autistic Society, London (1997) and data based on Wing

(1993) and Ehlers and Gillberg (1993) suggest that

Asperger syndrome may be much more common than

autism, there are no adequately standardised diagnostic

instruments specifically designed for this client group.

First, the few that do exist still require further research if

they are to demonstrate acceptable levels of validity,

reliability, specificity and sensitivity. Moreover, these are

mainly being developed as screening instruments only.

They do not aim to provide the clinician with the detail

and structure that the ADI-R, for example, offers for the

diagnosis of autism. Furthermore, each focuses on the

identification of higher functioning individuals within the

autistic spectrum. They are not designed to distinguish

between those with Asperger syndrome and those with

high functioning autism. Indeed, this may well be a

fruitless pursuit. Leekam et al. (2000) conclude that a

dimensional, rather than categorical approach to the

classification of autistic spectrum disorders is more ap-

propriate, and that ‘ it is time to move away from

potentially circular attempts to differentiate Asperger

syndrome and autism’. They also suggest that too rigid

adherence to specific diagnostic criteria can lead to the

exclusion of individuals from the services they need. Lord

(1997) notes that there is ‘an urgent need for instruments

that address diagnoses beyond autism, particularly

Asperger’s syndrome’. For practical purposes, however,

perhaps the most pressing need is for instruments that can

be used reliably to identify those individuals within the

autistic spectrum whose deficits are ‘milder ’, or more

subtle, and yet still have a major impact on their lives.

Second, it is unrealistic to assume that a single instrument,

no matter how thoroughly researched, can be used in

isolation to ascertain diagnosis. Detailed information on

cognitive and linguistic levels, family history, medical,

social, psychiatric and, if possible, genetic background

will also be required in order to differentiate autism

spectrum disorders from superficially similar conditions

that may result from different causes (e.g., Rutter et al.,

1999; Volkmar et al., 1999; Filipek et al., 1999). The

importance of clinical judgement and expertise must also

never be underestimated.

Finally, there can be little doubt that, at least in part, ‘ the

absence of replicable, reliable, and valid instruments in

this area is related to the absence of clear diagnostic

criteria for these disorders ’ (Lord, 1997). Unless problems

of classification can be satisfactorily dealt with in future

revisions of ICD and DSM, the development of effective

and reliable diagnostic instruments will continue to be

compromised.

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Assessment Instruments for Asperger Syndrome