Individuals with autism spectrum disorders (ASD) experience a range of vulnerabilities that span across areas of development, as well as vary throughout life. Thus, in order to accurately assess areas of need, a comprehensive, multidisciplinary evaluation is merited – oftentimes, at multiple developmental stages. This not only involves evaluating various areas of development, including developmental history, level of functioning, the nature and course of development over time, and ability to functionally apply one’s repertoire of skills to everyday life across settings and contexts, but more importantly entails effectively integrating and conceptualizing all of the results into one cohesive diagnosis (Klin, Carter, Volkmar, et al., 1997; Klin, Saulnier, Tsatsanis, & Volkmar, 2005). This process requires experienced clinicians who are knowledgeable of ASD, as well as clinicians who are familiar with the intricacies of child development.
Cognitive Assessment
The first and primary component of any evaluation involves obtaining a baseline of cognitive and/or developmental skills. The type of measure used to assess an individual’s cognitive profile depends on the age and level of functioning of the person. For very young children, a developmental assessment is indicated. Examples include the Mullen Scales of Early Learning (Mullen, 1995) and the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley, 2005). It is important to emphasize that although standard scores can be obtained on developmental measures, a young child’s abilities continue to change throughout early development and for this reason, interpretations or predictions about future levels of functioning based on early developmental profiles should be avoided.
Common measures to assess cognitive ability, or IQ, in older individuals include the Wechsler scales (e.g., the Wechsler Intelligence Scale for Children, Fourth Edition; WISC-IV, Wechsler, 2003) and the Differential Ability Scales, Second Edition (DAS-II; Elliott, 2007). Due to skill variability, as well as differences in attention to tasks, tolerance for task demands, and behavioral regulation, it is important to invest careful thought into the process of selecting appropriate instruments and testing procedures in order to ensure that results are valid. If a child is unable to complete an instrument that is standardized for his/her chronological age, oftentimes it becomes necessary to use instruments that are standardized for developmentally younger individuals.
Although standard scores might not be obtainable for the individual in question, the information gathered is quite useful for knowledge of strengths, weaknesses, behavior, and mental age. If a nonverbal measure of intelligence is used (e.g., the Leiter International Performance Scale, Revised; Roid & Miller, 1997), caution should be taken in interpreting results solely from one area of ability.
In special cases, additional neuropsychological or achievement testing is merited in order to identify any specific concerns related to attention, concentration, impulsivity, executive functioning, memory, motor planning, sensory-perceptual, or learning vulnerabilities. In such cases, the appropriate comprehensive assessments are indicated, usually upon referral.
Assessment of Adaptive Functioning
Another essential component of the diagnostic evaluation is assessment of functional or “real-life” skills. More often than not, individuals across the spectrum have great difficulty applying their repertoire of skills to naturalistic and daily contexts, regardless of level of ability or impairment. In fact, research has repeatedly shown that adaptive skills in autism fall substantially below cognitive ability, with the most significant deficits observed in social functioning (e.g., Carter, Volkmar, Sparrow, et al., 1998; Klin et al., 2007). One of the most widespread instruments to assess adaptive functioning is the Vineland Adaptive Behavior Scales, currently in its second edition (Sparrow, Cicchetti, & Balla, 2005). The Vineland measures self-sufficiency throughout the lifespan in the areas of adaptive Communication, Socialization, Daily Living, and Motor skills via a semi-structured interview with parents, primary caregivers, or teachers.
Although by definition, individuals with cognitive impairment have deficits in adaptive skills, it is less well known and often overlooked that most individuals with autism without cognitive impairment also have deficits in these areas – including in Asperger Syndrome (Saulnier & Klin, 2007). It is lack of independent, functional skills that tends to result in poor outcome in adulthood (Howlin, Goode, Hutton, & Rutter, 2004). Thus, there should be a focus on adaptive skills instruction in all intervention programs, and there is an indication that this instruction should intensify with age.
Communication Assessment
Communication skills in individuals with ASD also vary across age and functioning level. Accordingly, specific types of assessments are used to evaluate communicative abilities at the prelinguistic, early linguistic, and advanced language levels (Paul, 2005). Comprehensive speech and language assessments include measures to evaluate expressive and receptive language, nonverbal communication (e.g., response to and use of gaze, gestures, facial expressions), responsiveness to language, pragmatics (e.g., effective language use in social contexts), and prosody (e.g., rate, volume, tone, inflection of speech). For individuals with fluent speech, particular attention should be given to the assessment of linguistic skills (e.g., phonetics, phonology, morphology, syntax, semantics), metalinguistic skills (e.g., comprehension of nonliteral language such as inferences, idioms, multiple meanings, metaphors, irony, and humor), and conversational skills (e.g., topic management, turn-taking, and perspective taking; Klin, Sparrow, Marans, et al., 2000). It is important for evaluations to incorporate both standardized norm-referenced assessments as well as informal observation of the individuals’ communicative skills in more natural settings in order to obtain a holistic sampling of the individuals’ abilities.
Diagnostic Assessment
The diagnostic work-up of an individual with ASD is twofold in that it involves both a comprehensive developmental history conducted with the individual’s parents or primary caregivers and direct observation of the individual’s behavioral presentation in both structured and unstructured contexts. Both components involve assessing language, communication, and social interaction skills, as well as behavioral presentation, including any restricted, repetitive, sensory or perseverative interests, atypical patterns of behavior, and behavioral dysregulation. Ideally, having the parents participate in or observe the diagnostic assessment allows for additional information on the consistency of their child’s history, as well as presentation across settings, and their responsivity to novel situations and people.
Details on specific symptomatology related to ASD can be collected in various ways. Clinicians can ask parents direct questions based on the diagnostic criteria set forth in the Diagnostic and Statistical Manual, Fourth Edition, Text Revision (DSM-IV-TR; American Psychiatric Association, 2000), and/or they can utilize various scales, checklists or interviews that probe for similar behaviors. Currently, the most comprehensive, structured measure to obtain diagnostic and historic information relevant to ASD through parent report is the Autism Diagnostic Interview, Revised (ADI-R; Rutter, LeCouteur, & Lord, 2003). Though it was developed as a research instrument, the ADI-R is clinically useful in that it offers a comprehensive and structured way of collecting pertinent details related to a child’s early developmental history. Questions probe for onset of symptoms, development of language, communication, social, and play skills, and patterns of restricted interests, perseverative behaviors, and unusual interests that are characteristic of the disorder.
After gathering a detailed history, the next step of the diagnostic process is to directly observe and probe for symptoms within more naturalistic social contexts. Understanding the variability of an individual’s presentation across situations, contexts, and people is critical not only to the diagnostic process, but also to conceptualizing the individual’s range of strengths and vulnerabilities so as to determine appropriate intervention strategies.
The Autism Diagnostic Observation Schedule (ADOS) is a semi-structured observation measure that was created as a means of standardizing diagnostic evaluation for research purposes, but like the ADI-R, is also quite useful clinically (Lord, Rutter, DiLavore, & Risi, 1999). The ADOS consists of 4 Modules (with a fifth Toddler Module in development) that are based on language level and age, ranging from nonverbal or verbal toddlers to verbal adults, and it involves a series of probes to elicit spontaneous behaviors. In young children, the probes are more play based and involve highly motivating toys/activities that directly elicit social communicative behaviors such as requesting, shared affect, eye contact, gestures, joint attention, and reciprocity. For older, verbal individuals, the probes are more interview based, pressing for insight and awareness into social and emotional experiences.
Regardless of measure or method used to evaluate symptom expression and severity, no single measure can diagnose ASD in isolation. The diagnostic process entails integrating all pieces of information gathered across multiple assessments and making an informed, clinical interpretation. For this reason, it has become the standard in the field that ASD diagnoses are made through expert clinical judgment.
Clinical Diagnosis in Very Young Children
Current nosological systems (e.g., the DSM-IV) and diagnostic measures related to ASD (e.g., ADOS and ADI-R) work well for children over the age of 3, but they tend to be less effective in detecting autism symptomatology or risk factors in very young children (i.e, under the age of 2) or in children below a certain developmental level (e.g., 18 months). Yet, there is a strong focus within the field on early detection, and research has shown that when experienced clinicians do diagnose ASD in young children, the diagnoses tend to be stable over time (Chawarska, Klin, & Volkmar, 2008). Early risk factors or markers of ASD in young children include not only atypical developmental behaviors (e.g., language delay or atypical language development, sensory sensitivities, visual tracking and attention abnormalities), but also include the delay in or absence of normally developing milestones such as eye contact, social smiling, imitation, babbling, responsivity to name (e.g., Zwaigenbaum et al., 2005). Due to rapid developmental changes early in life, as well as the impact of intensive early intervention, diagnoses in very young children should always be considered provisional and re-evaluated over time. Furthermore, the gold-standard for diagnosing autism in infancy similarly involves the clinical judgment of experienced clinicians who are knowledgeable of both ASD and early child development, and when developmental information is gathered from multiple sources (e.g., Chawarska, Klin, Paul, and Volkmar, 2007).
Summary
In summary, the diagnostic evaluation of individuals with ASD involves a comprehensive multidisciplinary approach to assessing a person’s profile of abilities and then effectively integrating the results into one cohesive formulation. Areas to assess include speech, language, communication, social, motor, cognition, adaptive behavior, and psychological/psychiatric functioning, among others. Furthermore, the nature and course of the individual’s development over time must be considered, as well as the role of genetic, family, medical, and educational histories and how these might impact an individual’s presentation and the person’s ability to functionally apply one’s repertoire of skills to everyday life across settings and contexts. With multiple professionals from a wide range of disciplines becoming involved in the diagnostic process, it is imperative that there be open communication and consultation between professionals not only to ensure consistent representation of each individual assessed, but also to implement the most appropriate intervention based on that individual’s profile of needs.
