The Leicestershire Intellectual Disability Tool: A Simple Measure to Identify Moderate to Profound Intellectual Disability

Background It is often useful to ascertain whether adults have moderate to profound intellectual disability (approximate IQ < 50; developmental age <108 months) when deciding whether to refer to specialist or mainstream services. The aim of the present study was to develop a simple measure to estimate moderate to profound intellectual disability in adults with a potential need for specialist care. Materials and Methods Three hundred and twenty‐two individuals with information on home interviews from the Leicestershire Learning Disability Register were also assessed using the Vineland Adaptive Behaviour Scales. A variety of variables concerning intelligence, adaptive functioning and dependency were used to predict developmental age (as estimated from the Vineland) using backward stepwise regression. The derived equation formed the Leicestershire Intellectual Disability (LID) tool. A cut‐off point was chosen using a receiver operator characteristic (ROC) curve to achieve 95% sensitivity in identifying moderate to profound intellectual disability. Results Seven variables from the home interviews were found to predict estimated developmental age at the 10% level (P ≤ 0.1). When the tool was used to detect adults with moderate to profound intellectual disability, the area under the ROC curve was 0.93. The chosen cut‐off point was 95% sensitive and 65% specific. The positive predictive value was 95%, the negative predictive value was 65%, and the overall diagnostic accuracy was 91%. Conclusions These preliminary findings suggest that the LID tool may help to identify adults with moderate to profound intellectual disability among those with potential need for specialist care. Further evaluation is recommended.