The Development of a Screening Tool for Differential Diagnosis of Autism and Mental Retardation

Abstract

Differential diagnosis of autism and intellectual disability (formerly known as mental retardation) is getting more problematic because of the awareness of both autism and MR in recent clinical work. The overlap of symptoms/features of both disorders is one of the major causes of this problem. Using the phenomenological approach, the range of 92 symptoms/features were elicited from parents of 20 children (10 each of autism and ID). They were validated by ten experts (psychiatrists and clinical psychologists) to the degree to which each symptom is diagnostically related to Autism or ID. Sixty-six symptoms were identified as clearly belonging to one category or the other. Using as a base ratings, the scale was administered to 260 children (110 children with ASD and 150 children with ID) through an interview with the mother or the teacher of the child. The factor analysis of 66 symptoms resulted in two distinct factors. In addition, each of those 66 symptoms was tested on Mann Whitney U Test for its significance in differentiating the two disorders. Those symptoms were retained which had high factor loading (0.30 or greater) as well as were found statistically significant in differentiating the two conditions (p< 0.01). This produced two scales i.e. ASD Scale and ID Scale. The sensitivity, specificity, predictive values, and concurrent validity were found to be respectable. The results were discussed in terms of cultural implications, improvement in differential diagnosis, and a functional profile of the children that will be useful in developing training programs.