The accuracy of the Child and Adolescent Intellectual Disability Screening Questionnaire (CAIDS-Q) in classifying severity of impairment: a brief report

BACKGROUND: Severity of intellectual disability (ID) is associated with a range of outcomes for the individual and having an indication of severity can help inform support needs. Previous research has not evaluated whether screening tools can accurately ascertain severity category in addition to providing a red flag for the presence of ID. METHODS: We used multi-category receiver operating characteristic (ROC) analysis to assess whether the Child and Adolescent Intellectual Disability Screening Questionnaire (CAIDS-Q) could be used clinically to classify individuals (n = 191) aged between 12 and 18 according to British Psychological Society (BPS) categories of severity of impairment. RESULTS: The volume under the surface statistic (VUS) was 0.59. The optimal cut-points estimated based on the ROC surface and Youden Index provided correct classification probabilities for the severe, significant and non-ID groups of 0.44, 0.63 and 0.86 and 0.79, 0.29 and 0.88 respectively. CONCLUSIONS: While the CAIDS-Q can accurately discriminate between those with and without ID, and provides a heuristic for severity of ID, the results indicate that it does not reliably identify whether an individual falls into the severe or significant category of intellectual impairment