Many individuals with ASD are diagnosed after beginning formal education, as they encounter social and academic expectations embedded in large-group instruction systems. Identification of students who have ASD but do not have a cognitive or language delay is particularly problematic, with the average age of diagnosis at 12 years. Most early screens for Autism miss students with milder forms of ASD, especially those without cognitive delay.
Background:
An 89-item rating scale was constructed to identify “high-functioning” students who might be usefully referred for diagnostic assessment of autism. A clinical sample of 102 students with ASD enrolled in public schools in the province of British Columbia was obtained. Teachers and parents were asked to rate students on a four-point likert scale to develop norms. The results were compared with data from a matched sample of non-referred students in the province to validate the inventory.
Objectives:
The principal investigators sought to develop a scale that could be easily completed by respondents, would contain content that reflected current knowledge of ASD (qualitative information describing characteristics from both the DSM and the literature on ASD students is expanded in the manual), could be easily scored and interpreted by qualified personnel and would discriminate between students with ASD and students without ASD.
Methods:
An initial item pool was constructed, based on criteria in DSM-IV-TR and on a review of literature. After review of items and instructions by several teachers, a pilot study of 164 items, grouped into 14 “characteristics” (clusters) involving 60 students (20 students diagnosed with ASD, 20 students from the same classes without a diagnosis of ASD and 20 students with behaviour problems) was performed. Seventy-four items were discarded. Ninety items, grouped into 13 characteristics, were normed on a provincial clinical sample.
Results:
A clinical sample, stratified by geography and age and ASD gender distribution, was identified. Teachers and parents were asked to complete the revised scale. A matching sample of non-referred children was obtained (the participation rate for the NonASD sample was 66 % of the clinical ASD sample). One more item was deleted, leaving 89 items, grouped into 12 “characteristics.” Internal consistency reliability for the total score exceeded .9 for both groups of respondents for the clinical sample. Discriminant function analysis showed for both groups overall correct classification rates that exceeded 90 %, using total scores. A small group of behaviour-disordered students was also rated by teachers. Analysis of variance showed significant differences between all three groups. Mean scores of parents and teachers differed significantly from each other. Separate norms were constructed for each.
Conclusions:
The principal investigators suggest that the inventory is a valid and reliable scale that may be used as part of a decision-making process to facilitate referrals for diagnostic assessment of school-age children who are suspected of having ASD.