Although screening instruments for autism spectrumdisorders (ASD) are widely used, none have been simultaneously evaluated in anoutpatient setting in which the instruments are commonly used.

To assess if the reported high psychometric propertiesof screening instruments for ASD in adults also apply to the naturalistic outpatientsetting.

We tested the Ritvo Autism Asperger Diagnostic Scale(RAADS-R) and two short versions of the Autism Spectrum Quotient (AQ), the AQ-28 and AQ-10 in 210 patients referred for psychiatric assessment and 63 controlsin six outpatient settings in the Netherlands. Assessing clinicians were blind tothe RAADS-R and AQ scores. At the end of the study, the clinical diagnosis (ASDor no ASD) was related to the RAADS-R and AQ-scores collected prior to the assessments.

Of the 210 patients, 139 received an ASD diagnosis and71 received another psychiatric diagnosis. While the clinical groups differedfrom each other and the control group in their scores on each of these threeASD measures, the percentage correct diagnoses was rather low (RAADS-R 68%,AQ-28 and AQ-10 61%). Both the sensitivity and specificity of each of theseinstruments was insufficient, where the sensitivity of the RAADS-R was thehighest (73%) and the AQ short forms had the highest specificity (70 and 72%).

None of these instruments have a sufficient predictivevalidity to be used to predict clinical outcome in out-patients settings.