International Survey of Autism Spectrum Disorder Diagnostic Procedures

Background: Efficient diagnosis of Autism Spectrum Disorder (ASD) is essential for timely access to intervention services. The “gold standard” diagnosis of ASD is often multidisciplinary teams with structured observation and diagnostic interviews. However, differences in timing, personnel and diagnostic tools exist among centers.

Objectives: Since no universally accepted diagnostic method exists, we surveyed ASD centers to better understand current international practices. 

Methods: A diagnostic tool and protocol survey was emailed to centers serving children with ASD. We collected 178 surveys from all world regions that correspond in English.

Results: Most children (42%) are assessed between 3-6 years of age. Multiple disciplines are used in 97% of centers, with an average of 4 (SD=2) disciplines used at each center. Psychologists (89%), Speech/Language Specialists (71%), Pediatricians (63%) and Psychiatrists (48%) are the most commonly used disciplines. Centers (n=90) from non-English speaking countries (N-ENG) use more Psychiatrists (p<.05) and centers (n=88) from English speaking countries (ENG) use more Pediatricians (p<.05). When questioned about their assessment protocols, 80% of centers report using standard procedures. The most frequently reported diagnostic tools are the Autism Diagnostic Observation Schedule (ADOS/ADOS-2; 84%), Autism Diagnostic Interview (ADI-R; 57%), Modified Checklist for Autism in Toddlers (48%) and Childhood Autism Rating Scale (CARS/CARS-2; 46%). The ADI-R is used more in N-ENG countries (p=.05), but the ADOS is used more in ENG countries (p<.05). Additional psychological testing is done in 78% of centers. The most common tests reported examine Intelligence (62%), General Development (50%) and Adaptive Behavior (38%), while Speech/Language specific tests are only reported by 17% of centers. The most frequently used tests are the Wechsler Scales (57%) and Vineland Adaptive Behavior Scales (28%). N-ENG countries report more appointments [3.3 visits (SD=1.7) vs. 2.5 visits (SD=1.6); p< .05], however, both ENG countries [5.9 hours (SD=2.7)] and N-ENG countries (6.1 hours; SD=4.3) spend similar numbers of hours in appointments. The average number of weeks from referral to diagnosis is 25 weeks (SD=21) for all centers. Although wait time from first assessment visit to diagnosis is similar for ENG [7.5 weeks (SD=9.5)] and N-ENG countries [7.2 weeks (SD=6.5)], ENG countries have significantly longer wait times between referral and the first assessment visit [26.3 (SD=21) weeks vs. 9.5 (SD=12) weeks; p<.05]. Specifically, Canada [45 (SD=23) weeks] has significantly longer referral wait times (p<.05), even when compared to other ENG countries such as the United States [19 (SD=13) weeks], and other Commonwealth countries [23 (SD=21) weeks].

Conclusions: The majority of centers use multidisciplinary teams and report using interview and child observation tools. Results show ENG centers have significantly longer referral wait times, use more Pediatricians and use the ADOS more often. Conversely, N-ENG countries report using more Psychiatrists and the ADI-R more frequently. Despite more appointments in N-ENG countries, there are similar amounts of time spent in appointments and nearly equivalent wait times between first appointment and diagnosis for both ENG and N-ENG countries. ASD diagnostic centers will be interested in comparing their own procedures to our findings.