A novel screening instrument for the assessment of autism in German language: validation of the German version of the RAADS-R, the RADS-R

The Ritvo Autism Asperger Diagnostic Scale-Revised (RAADS-R) demonstrated excellent results in its original study, with a sensitivity of 97% and a specificity of 100% (Ritvo et al. in J Autism Dev Disord 41:1076-1089, 2011). As a result, it was included in the National Institute for Health and Care Excellence (NICE) guidelines (Recommendations | Autism spectrum disorder in adults: diagnosis and management | Guidance | NICE, 2022). The questionnaire includes 80 questions across four subcategories (language, social relatedness, circumscribed interests, sensory motor). So far, the subcategory sensory motor has not been addressed in most available instruments, despite being part of the diagnostic criteria specified in DSM-5 (Falkai et al., in Diagnostisches Und Statistisches Manual Psychischer Störungen DSM-5. Hogrefe, 2015) and ICD-11 (ICD-11 for Mortality and Morbidity Statistics, 2022). In our validation study, we tested a translated German version of the questionnaire in 299 individuals (110 persons with ASD according to ICD-10 F84.0, F84.5, 64 persons with an primary mental disorders (PMD), 125 persons with no disorders). To enhance the practical use of the instrument in clinical everyday practice, the questionnaire was completed by the participants without the presence of a clinician-unlike the original study. Psychiatric diagnoses were established following the highest standards, and psychometric properties were calculated using established protocols. The German version of the RADS-R yielded very good results, with a high sensitivity of 92.5% and a high specificity of 93.6%. The area under the curve (AUC = 0.976), indicates a high quality and discriminatory power of RADS-R. Furthermore, the ROC curve analysis showed that the optimal threshold to distinguish between the ASD and non-ASD groups in the German version of the RAADS-R is a score of 81. In comparison to the RADS-R, the co-administered instruments Social Responsiveness Scale (SRS), Autism Spectrum Quotient (AQ), and Empathy Quotient (EQ) each showed slightly better specificity but worse sensitivity in this sample.The study included individuals already diagnosed with ASD according to ICD-10 (F84.0, F84.5), with or without an primary mental disorders, preventing us from identifying the influence of comorbidities on the RADS-R results. In addition, a self-report questionnaire has generally only limited objectivity and may allow for false representation of the symptoms. The RADS-R compares well with other questionnaires and can provide valuable additional information. It could turn out to be a helpful diagnostic tool for patients in Germany. We propose naming the German version RADS-R (Ritvo Autism Diagnostic Scale - rRevised) to reflect the change in terminology.