comparison between diagnostic instruments for identifying high-functioning children with autism
TRANSCRIPT
Journal of Autism and Developmental Disorders, Vol. 24, No. 3, 1994
Comparison Between Diagnostic Instruments for Identifying High-Functioning Children with Autism 1
N u r i t Yirmiya z Hebrew University of lerusalera
Marian S i g m a n and Betty Jo F r e e m a n University of California, Los Angeles
Two instruments for identifying autism in children and adolescents with intellectual abilities in the normal range were compared. Diagnostic tools consisted of the Autism Behavior Checklist (ABC) and the Autism Diagnostic Interview (AD O . The sample was composed of 18 children who were all diagnosed as having either infantile autism or infantile autism, residual state based on DSM-III criteria by a clinical team using observations, parental interviews, and interactions with the children. Only 4 of the children met diagnostic cutoffs for autism on the current ABC but all met criteria for diagnosis on the ABC using parental recall of the child's behavior at 3-5 years of age. The ADI had somewhat greater specificity in that 3 children did not meet criteria for diagnosis although 2 of these children also received ABC scores based on parental recollection that were in the borderline range.
1Preparation of this paper was supported by NINCDS grant NS 25243 and NICHD grant HD 176620 to the second author. Special thanks are extended to Robin L. Gilmore, Mike Espinosa, Margie Greenwald, Larry Epstein, Mary Louise Bland, and Alma Lopez for assistance in various stages of the project; to Robert Asarnow and Linda Bott for diagnosing the children using DSM-III criteria; and to Lindi Martinez and Cory Shulman for their help with the ADI. We appreciate the cooperation of the families who participated in the study.
2Address all correspondence to Nurit Yirmiya, Department of Psychology, Hebrew University of Jerusalem, Mount Scopus, Jerusalem, Israel 91905.
281
0162-3257/94/0600-0281507.00/0 ~ 1994 Plenum Publishing Corporation
282 Yirmiya, Sigman, & Freeman
Researchers and clinicians working with autistic individuals use various in- struments to diagnose individuals with autism. Most of these diagnostic in- struments fall within the broad categories of questionnaires and checklists (e.g., Autism Behavior Checklist [ABC], Krug, Arick, & Almond, 1980); observational schedules (e.g., Autism Diagnostic Observation Schedule [ADOS], Lord et al., 1989; Autism Observation Schedule, Siegel, Anders, Ciaranello, Bienenstock, & Kraemer, 1986; Behavioral Observation System [BOS], Freeman, Ritvo, Guthrie, Schroth, & Ball, 1978; Freeman, Ritvo, & Schroth, 1984; Childhood Autism Rating Scale [CARS], Mesibov, Schopler, Schaffer, & Michal, 1989; Schopler, Reichler, DeVellis & Daly, 1980); and standardized interviews (e.g., Autism Diagnostic Interview [ADI], Le Couteur et al., 1989; Wing & Gould, 1978). Diagnostic evalu- ations typically involve some combination of systematic detailed develop- mental history, direct observation, and detailed psychometric measures.
Over the last decade or so, researchers have investigated the psy- chometric properties of some of the available instruments. Most of this research has focused on low-functioning (mentally retarded) autistic indi- viduals (Mesibov et al., 1989; Sevin, Matson, Coe, Fee, & Sevin, 1991; Teal & Wiebe, 1986; Volkmar et al., 1988). However, about 5-30% of all autistic individuals function within the normal range of intelligence (DeMyer, 1979; Freeman & Ritvo, 1984; Rutter & Schopler, 1987; Yirmiya & Sigman, 1991). Thus, the applicability of these instruments to the diagnosis of high- funct ioning individuals with autism has been quest ioned (Rut ter & Schopler, 1987).
The purpose of this study was to compare diagnostic instruments and clinical diagnoses for autism in a group of high-functioning (nonre- tarded) autistic individuals. The clinical diagnoses were based on Ameri- can Psychiatric Association (APA, 1980) criteria for infantile autism and infantile autism, residual state since the children were diagnosed before DSM-III-R (APA, 1987) was published. The diagnostic instruments con- sisted of the ABC (Krug et al., 1980) and the ADI (Le Couteur et al., 1989).
Based on previous suggestions (Krug et al., 1980; Wadden, Bryson, & Rodger, 1991) that concurrent ABC scores may not be appropriate for older high-functioning autistic individuals, parents were requested to com- plete the ABC based on behavior when their children were 3-5 years of age in addition to the ABC that they completed for their children's current behavior. Past medical records from the time that the children were 3-5 years old were examined to evaluate and establish the validity of parental retrospective reports. Finally, possible differences between children diag- nosed with infantile autism, full syndrome, and those diagnosed with in- fantile autism, residual state based on DSM-III criteria were examined.
High-Functioning Autism: Diagnosis 283
METHODS
Subjects
Eighteen children (17 male, 1 female) participated in the study. Chil- dren ranged in age from 9 years, 3 months to 16 years, 10 months (M = 149.94 months, SD = 26.10; see Table I for subjects' description). The sam- ple was ethnically diverse and comprised 10 Caucasian, 4 Hispanic, 2 Af- rican-American, and 2 Asian children. Subjects were recruited from the UCLA Center for Research on Childhood Psychosis and from other clini- cians working at UCLA.
The children were diagnosed within 2 years prior to the study by one or more clinicians not affiliated with the present research program. Diag- noses of the children with autism were made by clinicians who diagnosed these children and other groups of children with psychotic disorders and mental retardation for ongoing research projects. Although the sample re- ported in this study involves subjects with autism only, it is unlikely that there was a bias toward diagnosing autism since children with other disor- ders were also diagnosed.
The DSM-III symptoms of autism were pervasive lack of responsive- ness to other people, gross deficits in language development, bizarre re- sponses to various aspects of the environment, and onset prior to age 30 months. These criteria are essentially consistent with Rutter's (1978) crite- ria. The clinical team used parental interviews and observations and inter- actions with the children. Based on these criteria, 11 children were diagnosed with infantile autism and 7 children were diagnosed with infan- tile autism, residual state. The latter diagnosis implies that the subject met all criteria for infantile autism in the past but no longer does so.
The ADI became available 15 months after the initiation of the pro- ject. At that time, subjects were located and their parent/s were requested to return to our laboratory for the interview. Three families had moved without leaving any forwarding information. Of the 3 children who were not located, 2 were diagnosed by the clinical team with infantile autism, and 1 was diagnosed with infantile autism, residual state. Subjects had to have a Full-scale IQ score on the Wechsler Intelligence Scale for Children- Revised of at least 75 to be included in the study.
Autism Behavior Checklist
The ABC (Krug et al., 1980) is a 57-item checklist of variably weighted behaviors that has been successfully used in making differential
284 Yirmiya, Sigman, & Freeman
diagnoses of autism (Teal & Wiebe, 1986). The ABC is broken down into 5 scales: Sensory; Relating; Body and Object use; Language; and Social and Self-help skills. Increased weight is given to those items that are more characteristic of autism. ABC scores are derived by adding the weights of all endorsed items for each of the 5 scales, as well as summing the 5 scale scores into a total score. Higher ABC scores are suggestive of an individual with many behaviors symptomatic of autism.
A score of 68 and above is associated with a high probability of clini- cal diagnosis. In the standardization sample, 90% of the sample who re- ceived ABC scores higher than 68 also had a previous diagnosis of autism. In contrast, 95% of the sample who received ABC scores lower than 53 were not diagnosed as autistic by clinicians (Krug et al., 1980).
Validity of the Retrospective ABC Ratings
Parental retrospective reports may be biased because parents may tend to recall fewer symptoms if their children are currently functioning well. To examine this possibility and to validate the parental retrospective reports, an independent rating, using information in medical charts re- ported when the children were ages 3-5 years old, was carried out. A trained investigator unfamiliar with the children contacted the parents and obtained their consent to review medical charts and reports about the chil- dren when they were 3-5 years old. Written materials were available for 10 of the 18 children.
The investigator familiarized herself with the written material and completed an ABC for each child. Only items that were clearly documented in the reports were endorsed so that many items could not be rated. The investigator was able to endorse an average of 24 items per subject (range 16-36). The parental retrospective ABC ratings correlated significantly with the investigator's ABC ratings, r = .72, p < .05. Thus, subjects who were rated on the ABC as having more severe autistic symptoms when they were 3 to 5 years old by their parents, based on the parents' recollections of the children, also were rated as having more severe symptoms by the investi- gator completing the ABC using the archival medical data for that age period. The obtained correlation suggests that parental retrospective re- ports about behaviors characteristic of their children are valid, and thus may be used to gather information about past behaviors and symptoms.
Tab
le I
. S
ampl
e C
hara
cter
isti
cs:
Age
, IQ
Sco
res,
AB
C S
core
s, a
nd D
iagn
oses
Ag
e C
hild
(m
onth
s)
Ver
bal
Per
form
ance
Fu
ll sc
ale
Ear
ly c
hild
hood
L
ate
chil
dhoo
d IO
IQ
IO
A
BC
~ A
BC
-'a
Dia
gnos
is
AD
I D
SM
-III
1 17
7
2 16
2
3 16
8
4 17
0
5 12
4
6 16
5
7 13
8
8 12
7
9 11
1
10
164
11
153
12
153
13
116
14
130
15
202
16
129
17
123
18
186
85
126
103
66
46
74
80
75
130
50
97
74
85
97
25
115
104
111
91
28
125
112
122
58
17
86
117
100
86
34
88
111
99
116
46
131
121
129
96
51
139
117
131
101
52
123
141
136
64
5
91
106
98
79
7
88
101
93
95
7
82
121
100
94
49
96
112
103
96
57
74
81
76
123
93
74
95
83
85
65
107
109
109
82
26
100
67
81
94
75
Aut
ism
A
utis
m
Aut
ism
A
utis
m
Aut
ism
R
esid
ual
Aut
ism
R
esid
ual
Not
A
utis
m
Aut
ism
R
esid
ual
Aut
ism
A
utis
m
Aut
ism
R
esid
ual
Not
A
utis
m
Not
R
esid
ual
Aut
ism
A
utis
m
Aut
ism
A
utis
m
Aut
ism
A
utis
m
Aut
ism
R
esid
ual
Aut
ism
A
utis
m
Mis
sing
R
esid
ual
Mis
sing
A
utis
m
Mis
sing
A
utis
m
a C
utof
f sc
ores
for
aut
ism
on
the
AB
C ~
68
; fo
r bo
rder
line
aut
ism
= 5
4.
286 Yirmiya, Sigman, & Freeman
Autism Diagnostic Interview
The ADI (Le Couteur et al., 1989) is a standardized investigator- based interview that is administered to the individual's primary caregiver by a trained interviewer. It emphasizes detailed descriptions of behaviors that focus on developmental deviance rather than on developmental delay. It is appropriate for use with both low-functioning and high-functioning individuals with autism between the ages of 5 years and early adulthood (mental ages >_2 years). The ADI focuses on three areas: reciprocal social interaction; communication and language; and repetitive, restrictive, and stereotyped behaviors.
The authors operationalized a working algorithm based on ICD-10 criteria to convert the responses into a diagnosis of autism. The algorithm is based on 14 items from the reciprocal social interaction domain; 12 items from the language/communication domain; 6 items from the domain of re- petitive, restricted, and stereotyped behaviors; and 4 items from the domain assessing evidence for deviant behavior prior to age 36 months. These items describe current as well as lifetime behaviors. To be diagnosed as autistic, verbal individuals must score above established cutoff scores on reciprocal social interaction (cutoff score = 10); communication and language (cutoff score = 8); and repetitive, restrictive, and stereotyped behaviors (cutoff score = 4). In addition, they must show evidence of developmental devi- ance prior to age 36 months (Le Couteur et al., 1989).
Procedures
Informed consent was obtained from parents and children. The chil- dren and their parent]s were seen twice for about 90 minutes each visit. The children completed standardized and experimental tasks (Yirmiya, Sig- man, Kasari, & Mundy, 1992) while parents completed several question- naires. The order of administration of the retrospective and concurrent ABCs was counterbalanced over the two sessions. An experienced research assistant was available to assist the parent in completing the ABCs. While the ABC is more commonly completed by teachers who are familiar with the child's behavior, the manual endorses parental reports with assistance from professionals.
The original ABC form has the weights associated with each item and the item's group clearly marked on the form. For example, the item "whirls self for long periods of time" has a weight of 2 points and belongs to the group of items regarding Body Concept. Following Volkmar et al. (1988), we deleted the particular weight and component group of each item
High-Functioning Autism: Diagnosis 287
from the form. In addition, the form was titled "Behavior Checklist" rather than Autism Behavior Checklist so that parents would not necessarily as- sociate this checklist with autism.
The ADI became available about a year after ABC data were collected. An interviewer who did not participate in earlier data collection and who was unfamiliar with the children called the parents to request that they return for a visit to our laboratory to complete the ADI. This interviewer had ex- perience with autism but was not formally trained on the ADI, because at the time no formal training courses were available.
All parents agreed to be interviewed with the ADI. All interviews were audiotaped. Since the ADI is a lifetime assessment it was assumed that even though it was collected 15 months after the initiation of the pro- ject, the results were reliable and could be compared with other diagnostic tools.
Two interviewers were trained to use the ADI by one of the original ADI authors (C.L.). After rating two tapes and receiving feedback from C.L., 4 additional tapes provided by C.L. were rated independently by the two interviewers who agreed between themselves and with C.L. regarding the presence or absence of the diagnosis of autism. A reliability check on 7 randomly chosen interviews was then carried out between the original interviewer, who interviewed and coded the 15 interviews reported in this paper, and 2 trained interviewers, one of whom participated in a formal course in London. Interrater agreement was 100% with regard to the di- agnosis of autism with 5 cases receiving diagnoses of autism and 2 cases not receiving diagnoses of autism. Intraclass correlations for algorithm ar- eas were very high and significant: .99 for reciprocal social interaction, .98 for language/communication, .96 for restricted, repetitive, and stereotyped behavior, and .99 for total algorithm score. The reliability estimates (kappa) for the individual algorithm items ranged from .54 to 1.00 with 23 of the 36 items revealing 100% agreement and kappas of 1.00.
RESULTS
Subjects' ages, WISC-R scores, ABC scores, ADI diagnoses, and DSM-III diagnoses are presented in Table I. Based on DSM-III diagnostic criteria, 11 subjects were diagnosed with infantile autism and 7 subjects were diagnosed with infantile autism, residual state. Scores on the ABC completed retrospectively for when subjects were between the ages of 3 to 5 years indicated that 15 of the 18 children received scores typical for chil- dren diagnosed with autism. The remaining 3 children received scores be- tween 54 and 67, which are in the borderline range (Krug et al., 1980).
288 Yirmiya, Sigman, & Freeman
Thus, all 15 subjects with available ADI data, were diagnosed as autistic, autistic-residual, or borderline autistic based on DSM-III criteria and ABC retrospective ratings for ages 3 to 5 years.
A different picture emerged for ABC ratings completed for cur- rent behaviors (late childhood). As can be seen from Table I, only 2 subjects scored above the suggested cutoff score of 67, while another 2 subjects scored in the borderline range. The remaining 14 subjects all scored below 54. Thus, according to current ABC ratings for late childhood, 14 children would no longer be diagnosed as autistic based on this instrument.
The ADI algorithms concurred with a diagnosis of autism for 12 of the 15 subjects for whom the data were available. Three subjects did not meet one or more of the four cutoff scores for autism and thus were not identified as autistic by the ADI. All 3 children did not meet cutoff criteria for the repetitive, restricted, and stereotyped behavior domain. The cutoff criteria for this area is 4. Two of the 3 children received scores of 3 while the third child received a score of 1. In addition, 2 of the 3 children did not meet criteria for the reciprocal social interaction domain. Both children received very low scores on this domain (a score of 1 and 2 when the cutoff score is 10). It is interesting to note that these 3 children were 3 of the 4 most intelligent children in the sample.
Examination of the data in Table I reveals that 2 of the 3 subjects who did not meet the ADI criteria for autism had DSM-III diagnoses of infantile autism and the third subject had a diagnosis of infantile autism, residual state. Furthermore, 2 of the 3 received retrospective ABC scores in the borderline range.
According to DSM-III criteria, individuals diagnosed with infantile autism, residual state may be expected to function better than individuals who meet the full criteria for infantile autism. To test this hypothesis, t tests were computed to compare the 11 subjects diagnosed as autistic and the 7 subjects diagnosed as autistic, residual state. In this sample, individuals diagnosed with infantile autism, residual state did not differ from individuals diagnosed with infantile autism on chronological age, Verbal IQ, Performance IQ, Full-scale IQ, overall summary ADI score, or either ABC score.
However, when individual area scores were examined, the 9 children diagnosed with infantile autism had a significantly poorer score, M = 14.11, SD = 4.34, on the communication and language domain of the ADI than the children diagnosed v~ith infantile autism, residual state, M = 10.33, SD - 2.94, t(13) = 1.85, p < .05, and on the retrospective ABC language scale, M --- 21.89, SD = 6.85, for the children diagnosed with infantile autism versus, M = 13.17, SD = 6.97, for the children diagnosed with autism, residual state, t(13) = Z40, p < .05. Regarding the ctment ABC scores,
High-Functioning Autism: Diagnosis 289
only one significant difference on the sensory scale emerged with the chil- dren diagnosed with autism, M = 7.44, SD = 6.64, receiving higher scores than the children diagnosed with the residual state, M = 1.50, SD = 2.81, t(13) = 2.05, p < .05. The higher scores on all indices indicate poorer functioning for the children diagnosed with autism versus those diagnosed with autism, residual state.
DISCUSSION
In this study, retrospective parental reports of their childrens' autistic symptoms at age 3-5 years revealed that all of the subjects received scores that indicated autism or borderline autism. Furthermore, parental retro- spective reports on childrens' symptoms and behaviors associated with autism were validated. Thus, based on this study, retrospective ABC ratings can be used to gather reliable information about the presence of autistic symptoms during early childhood.
In contrast to the finding that all subjects met the cutoff score for autism or borderline autism on retrospective ratings, current ABC ratings endorsed for the same children for current symptoms reveal that 14 of the 18 children received scores below the cutoff score for autism or borderline autism. Therefore, given that the authors of this checklist (Krug et al., 1980) expressed some concerns about the applicability of the ABC to high-func- tioning individuals with autism, and that these current ratings ruled out autism in children who received this diagnosis based on current DSM-III criteria and according to the ADI, a more plausible explanation may be that this instrument is not appropriate for use with school-age autistic children who function in the normal intellectual range. Support for this position comes from a study by Wadden et al. (1991) which included 16 nonretarded children in the autistic sample. The ABC did not agree with other diagnostic criteria when the recommended cutoffs were used. The authors point out that 9 of 16 children who were rated as unlikely to be autistic were func- tioning at relatively high intellectual levels.
Using the clinical diagnosis as the criterion, the early ABC ratings were the more sensitive of the two measures in that all subjects received diagnoses of autism or borderline autism. The ADI was more specific in that diagnosis was ruled out for 3 subjects, Several explanations for the difference in diagnosis for the 3 subjects can be suggested. First, the 3 chil- dren who did not receive a diagnosis were 3 of the 4 most intelligent chil- dren in the sample (IQs of 122, 131, and 136). It may be that the ADI is somewhat insensitive in diagnosing very intelligent autistic individuals. Second, clinical diagnoses using DSM-III included observations of and interviews
290 Yirmiya, Sigman, & Freeman
with the children. The ADI may need to be supplemented with these meas- ures in some cases, and the authors have formulated the ADOS (Lord et al., 1989) for this purpose. It should be pointed out that there is now a new version of the ADI, the ADI-R, in which the social criteria have been expanded and the criteria for the repetitive, restricted behavior have been made less stringent in line with DSM-IV and ICD-10.
To check on the clinical diagnoses of these 3 children their medical records were examined. One child was hospitalized after this study was com- pleted, and her diagnosis confirmed by the hospital staff. A second child was described in his last assessment as suffering from great social difficulties, severe obsessions, and problems with understanding and using language in social situations, suggesting that the diagnosis was correct. The third child seems to have recovered almost completely according to the descriptions of him as an adolescent. However, by as late as 41/2 years of age, he showed multiple repetitive, restrictive behaviors and was nonverbal. Thus, the medi- cal records suggest that all 3 children were correctly diagnosed as autistic in early childhood and that 2 of them clearly remain so. It may be that the functioning of these children improved so much from early years that the responses of the parents to the ADI underestimated both their early and later problems, although they could remember back accurately when asked to describe their children at ages 3--4 years on the ABC.
Finally, children diagnosed with infantile autism were not found to differ from children diagnosed with infantile autism, residual state on the demographic variables nor on the overall summary ADI score or the total ABC scores. These data may be interpreted as supporting the decision to eliminate the diagnostic category of infantile autism, residual state from DSM-III-R. However, closer examination reveal that these two groups of children differ in their communication and language abilities as manifested in both the ADI and ABC. In addition, other data (Yirmiya et al., 1992) suggest that these two groups of children differ on social/affective variables rather than on cognitive and demographic variables such as those included in the current study. DSM-III-R (APA, 1987) includes the diagnostic cate- gories of autistic disorder and pervasive developmental disorder. Future studies should address the usefulness of this differentiation as well as the unique characteristics of individuals who receive these diagnoses and the differences among them.
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