Cognitive assessment using the Rapid Assessment for Developmental Disabilities, Second Edition (RADD‐2)

Abstract

Background Individuals with developmental disabilities (DD) often have severe impairments and maladaptive behaviours that make it difficult to reliably assess their cognitive abilities. Given these challenges, the Rapid Assessment of Developmental Disabilities, Second Edition (RADD‐2), was designed to measure general cognitive ability in this population. The purpose of this study is to demonstrate the battery's psychometric properties when used with individuals with DD who have challenging behavioural and psychiatric conditions and for those who have limited verbal skills. Method The cognitive and adaptive behaviour skills of 193 children and adults with DD and considerable medical, behavioural and/or psychiatric problems were evaluated using the first and second editions of the RADD, Kaufmann Brief Intelligence Test – 2nd Edition, and Scales of Independent Behaviour – Revised Edition. Medication side effects and challenging behaviours were assessed using the Aberrant Behaviour Checklist. Results There were no floor or ceiling effects on the RADD‐2. Both the nonverbal index and total scores had strong concurrent validity with other abbreviated tests of intellectual ability and good discriminant validity from measures of adaptive behaviour and medication side effects. RADD‐2 scores also had strong criterion validity as they successfully differentiated between all levels of intellectual functioning. Age and sex did not differentially affect RADD‐2 performance, and the co‐occurrence of psychiatric conditions did not negatively affect performance. The only medical condition associated with lower RADD‐2 performance was epilepsy. Conclusions The RADD‐2 can quantify the differential cognitive abilities of individuals with DD, even for those with minimal communication skills, challenging behaviours or severe medication side effects that can typically complicate assessment. This brief cognitive battery can be used to measure changes due to interventions, on the one hand, and progression of neurological disease, on the other.

Development and validation of a functional screening tool for adults with intellectual disabilities

“…Considering assessing the functional abilities of individuals with functional disabilities, DSPs have the ability to recognize even small changes in their service recipients, as a result of their day-to- The FST-ID allows direct service providers to become active partners in the decision-making process of care for their service recipients (Manduchi et al, 2020;Oudshoorn et al, 2021) by identifying their functional status with more than 90% accuracy. Having an accurate understanding of a person's functional abilities in their environments is an important aspect of the FST-ID (Hom et al, 2021), and in view of the new instrument's strong psychometric properties, online accessibility, and short completion time (around 5 min per service recipient), it may be considered a useful tool in clinical service.…”

“…The RADD-2 is a relatively short tool, containing 76 items, constructed mainly for cognitive assessment of intellectual disabilities. It is designed to be used by healthcare professionals; therefore, it is not suitable for use by direct care providers (Hom et al, 2021).…”

“…Therefore, it is not suitable as a screening tool, although it certainly can serve as the foundation for constructing such a tool. In summary, the currently available instruments, are not suitable as a screening tool for practical use by primary care providers (Hom et al, 2021; Icht et al, 2021; Kadari & Shiri, 2015; Manduchi et al, 2020).…”

“…Another issue recently introduced was the need to consult with primary care providers when introducing therapeutic changes (Manduchi et al, 2020) because of their deep familiarity with the service recipients, especially with individuals with severe/profound intellectual disabilities. An appropriate screening tool may assist care providers to detect changes without increasing their workload, especially in individuals with severe/profound intellectual disabilities, who lack appropriate assessment tools tailored to their unique and numerous communicational, physical and social accessibility needs (Hom et al, 2021; Kadari & Shiri, 2015). When developing a short screening tool for detecting the functional state of adults with intellectual disabilities, the most useful instruments are those that are as brief as possible and easily comprehensible (Beaton & Grimmer, 2013).…”

“…Establishing the validity and reliability of such a short tool is also extremely important to minimise measurement errors (Barhak, 2013; Hom et al, 2021). Therefore, the new tool must present content validity (Lotan et al, 2009) and concurrent validity against a well‐established, valid, and reliable test (gold standard) such as the ABAS‐II (Oakland et al, 2013).…”