Diagnostic Assessment of Autism Spectrum Disorder: A Cross-Disciplinary Analysis

Background: Currently, there are no known biological markers that can accurately diagnose Autism Spectrum Disorder (ASD) (Huerta & Lord, 2012). As such, diagnosis generally relies on behavioural observations and assessment. While best practice guidelines exist (Anagnostou et al., 2015; Volkmar et al., 2014), very little is known regarding the actual assessment and diagnostic practices of clinicians who diagnose ASD. The limited research that does exist, indicates that assessment practices are variable, dependent on the clinician’s profession (i.e., medicine or psychology), and may not adhere to best practices such as multidisciplinary team assessment or the use of standardized assessment measures (Skellern, McDowell, & Schluter, 2005; Taylor et al., 2016; Ward, Sullivan ,& Gilmore, 2016). This paucity in research is troubling, given that an ASD diagnosis has major implications for individuals being diagnosed, as well as for their families, providing access to a variety of supports and services.

Objectives: The purpose of this study was to examine the assessment procedures of Canadian psychologists and physicians who diagnose ASD in childhood. In addition, the study aimed to ascertain whether these assessment procedures changed depending on the perceived or actual cognitive functioning of the child they were assessing.

Methods: Participants from two professions: psychology and medicine were recruited using snowball sampling. To recruit Canadian psychologists and physicians, professional associations throughout Ontario were contacted and asked to disseminate the study to their members. Participants were asked to complete an online questionnaire regarding their assessment and diagnostic practices including their professional experience, multidisciplinary team use, their broad assessment procedures, as well as their use of specific ASD assessment tools. Sixty-two participants (41 psychologists and 23 physicians) completed the survey.

Results: Assessment and diagnostic practices of the participants varied depending on their profession. Psychologists indicated a greater reliance on standardized measures of intelligence, adaptive functioning, and ASD symptomatology. Physicians reported a greater reliance on unstructured observation, as well as on medical testing (i.e., genetic and audiological assessment). Both groups reported relatively low levels of multidisciplinary team involvement, and those who did indicated that a second member of their own profession was most often part of their assessment team. Both groups reported a greater reliance on unstructured observation as well as use of the Childhood Autism Rating Scale (CARS) when assessing children with lower perceived cognitive abilities, and a greater reliance on the Autism Diagnostic Interview- Revised (ADI-R) when assessing children with average or above perceived cognitive abilities.

Conclusions: The current study highlights the need for further investigation into the assessment and diagnostic practices of clinicians who diagnose ASD. Inconsistent assessment methodologies between diagnosticians could result in decreased diagnostic reliability, impacting both clinical and research initiatives. For instance, failure to rely on best practice could result in a child not receiving needed intervention services. Further, given the variation in assessment procedures based on the cognitive abilities that was reported, the study highlights the need for research into the utility of assessment battery variations based on a child’s cognitive ability.