Looking back, looking forward: Methodological challenges and future directions in research on persons with profound intellectual and multiple disabilities

Within the context of the Special Interest Research Group (SIRG) on Persons with Profound Intellectual and Multiple Disabilities (PIMD), researchers often discuss the methodological problems and challenges they are confronted with. The aim of the current article was to give an overview of these challenges. The challenges are centred on six topics. These reflect the main components of a study's design: (a) participant demarcation, (b) participant recruitment, (c) data collection and instruments, (d) data analysis, (e) ethics/including the “voice” of persons with PIMD and (f) theoretical models. Next, to describing the specific challenges, possible solutions and pathways to address them are discussed. These are illustrated by recent studies by the authors and other researchers in the field. The current contribution wants to stimulate further discussion and ex-change of ideas, and the development of creative research techniques

The PDD-MRS:An instrument for identification of autism spectrum disorders in persons with mental retardation

The Scale of Pervasive Developmental Disorder in Mentally Retarded Persons (PDD-MRS) is described. The PDD-MRS is a simple classification and screening instrument devised for identification of autistic disorders (of the entire spectrum) in persons with mental retardation from mild to profound levels, age-range 2-55 years. The norms of the scale are based on the research protocols of 1230 Dutch persons with mental retardation. The scale's sensitivity for the entire normative sample was found to be 92.4%; calculated separately for persons at all levels of mentally retarded functioning, male and female persons, speaking and non-speaking persons and five age categories, the sensitivity figures range between 87.0 and 100.0%. The specificity of the scale is also 92.4%; for the aforementioned subgroups separately, the specificity figures range between 84.6 and 95.5%. Roughly similar values for sensitivity and specificity were found when using the scale with severely visually impaired/blind persons; severely hearing-impaired/deaf persons; persons with Down syndrome; male persons with fragile X syndrome. The original version of the PDD-MRS dates from 1990; since then the scale has been widely used in the Netherlands and Belgium. The PDD-MRS should be regarded as a useful instrument for identifying PDD in persons with mental retardation

Prevalence of pervasive developmental disorders in children and adolescents with mental retardation

Background: Insight into the prevalence of pervasive developmental disorder (PDD) in children and adolescents with mental retardation (MR) is known to be of clinical importance. However, estimating this prevalence is complicated. The literature reports prevalence rates ranging from 3% through 50%. This variation seems to be related to the concepts of PDD under study, the instruments used, and the studied populations. The present study aimed to estimate a reliable prevalence rate of PDD. Methods: A total population-based screening with the PDD-MRS and the ABC (n = 825) was followed by further assessment of children and adolescents at high risk for PDD according to these instruments, and for controls, with the ADI-R, ADDS-G and a DSM-IV-TR classification (n = 188). Results: The instruments lead to different prevalence rates that range from 7.8% to 19.8%. The differences in the estimated prevalence rates are related to the concept of PDD and the instruments they represent. The DSM-IV-TR prevalence (16.7%) seems to be the most reliable and well-founded estimate, since this prevalence rate is based on information from multiple informants and multiple time periods. Conclusions: The reported prevalence rates provide policy makers with an up-to-date and more substantiated guideline for the allocation of resources for children and adolescents with MR and PDD. The height of the prevalence should alert professionals that PDD is widespread in the population with MR. Keywords: Prevalence, PDD, MR

The psychometric properties of the Vineland Adaptive Behavior Scales in children and adolescents with mental retardation

The psychometric properties of the Vineland Adaptive Behavior Scales Survey Form were studied in a total population of children and adolescents with MR, and in the specific levels of functioning (n = 826, age 4-18 years). The original division into (sub)domains, as assigned by the authors, was replicated in the total population and in the mild and moderate levels of functioning. In the severe and profound levels of functioning the structure was less well recognized. The reliability of the instrument proved to be good in the total population and the subgroups. The construct validity was high in all groups. The implications of these findings are discussed with respect to the usefulness of the Vineland for the population with MR

Adaptive functioning and behaviour problems in relation to level of education in children and adolescents with intellectual disability

Background The interrelationship between adaptive functioning, behaviour problems and level of special education was studied in 186 children with IQs ranging from 61 to 70. The objective was to increase the insight into the contribution of adaptive functioning and general and autistic behaviour problems to the level of education in children with intellectual disability (ID). Methods Children from two levels of special education in the Netherlands were compared with respect to adaptive functioning [Vineland Adaptive Behavior Scales (VABS)], general behaviour problems [Child Behavior Checklist (CBCL)] and autistic behaviour problems [Autism Behavior Checklist (ABC)]. The effect of behaviour problems on adaptive functioning, and the causal relationships between behaviour problems, adaptive functioning and level of education were investigated. Results Children in schools for mild learning problems had higher VABS scores, and lower CBCL and ABC scores. The ABC had a significant effect on the total age equivalent of the VABS in schools for severe learning problems, the CBCL in schools for mild learning problems. A direct effect of the ABC and CBCL total scores on the VABS age equivalent was found, together with a direct effect of the VABS age equivalent on level of education and therefore an indirect effect of ABC and CBCL on level of education. Conclusions In the children with the highest level of mild ID, adaptive functioning seems to be the most important factor that directly influences the level of education that a child attends. Autistic and general behaviour problems directly influence the level of adaptive functioning. Especially, autistic problems seem to have such a restrictive effect on the level of adaptive functioning that children do not reach the level of education that would be expected based on IQ. Clinical implications are discussed