A Scale to Assist the Diagnosis of Autism Spectrum Disorders in Adults: (RAADS-R) An International Multi-Center Standardization Study

Background: The initial version of the Ritvo Autism Asperger Diagnostic Scale (RAADS), designed to assist the diagnosis of Autism Spectrum Disorders (ASD) in adults (18 years and older), contained 78 questions. Published data (1,2) demonstrated it to be reliable, sensitive, and specific in a limited number of subjects. Questions assessed developmental pathology in three symptom areas: language, relatedness, and sensory-motor (following DSM IV-TR criteria). After critical review, a new 80-item version was developed (RAADS-R) with the addition of two questions, several word clarifications and the addition of a circumscribed interests question domain.

Objectives: To present the results of the international multi-center standardization study of the new 80-item version, the RAADS-R.

Methods: 200 ASD subjects were diagnosed at nine medical centers, in four countries, by these research criteria: 1) A clinical interview (must meet each center's criteria). 2) ADI/ADOS or at least ADOS module 4 to assess validity. 3) Standardized IQ test. 4) Constantino SRS-A in a subset of subjects to assess validity. 5) Repeat testing in 50 subjects, a mean of 15 months later, to assess reliability. Comparison subjects: 1) 285 Volunteers without a DSM IV diagnosis. 2) 302 Volunteers with current DSM IV TR diagnosis other than ASD.

Results: The RAADS –R is highly valid, reliable, sensitive (.98), and specific (1). Statistical analysis revealed no significant difference between Autistic and Asperger subjects' mean RAADS-R scores. Test-retest results showed no significant differences in scores in both groups. Cronbach’s alpha coefficients were computed for each of the question domains and were satisfactory. Factor analysis and Ancova results will be reported.

Conclusions: The RAADS-R is a highly valid and reliable instrument used to assist clinicians diagnosing adults 18 and older with ASD. The RAADS-R demonstrates higher sensitivity with individuals who have insight. It is less sensitive in younger subjects, 18-21 year-olds  who show a tendency to deny symptoms. Also, it appears that more affected individuals are  less likely to be accurate reporters. This needs to be studied further. Translations of the RAADS-R into Swedish and Japanese are completed and standardization studies are nearing completion. Translations into Hindi and French are in early stages.

Participating centers are: Yale, USA; Mt. Sinai, USA; University of Utah, USA; Monash University, Australia; UCLA, USA; Griffith University, Australia; ASPECT, Australia; Geneva Center, Canada; King’s College, England; Karolinska Institute, Sweden; Hamamatsu University, Japan.  

References: 1) A Scale to Assist the Diagnosis of Autism and Asperger Disorder in Adults (RAADS): A Pilot Study. Ritvo RA, Ritvo ER, Guthrie D, Yuwiler A, Ritvo MJ, Weisbender J. Autism Dev Discord (2008) 38: 213-223. 2) Clinical Evidence That Asperger Disorder is a Mild Form of Autism. Riva Ariella Ritvo, Edward R. Ritvo, Donald Guthrie, Max J. Ritvo Comprehensive Psychiatry, (2008) Volume 49, Issue 1, January-February.