Measurement invariance in the assessment of people with an intellectual disability

Intellectual assessment is central to the process of diagnosing an intellectual disability and the assessment process needs to be valid and reliable. One fundamental aspect of validity is that of measurement invariance, i.e. that the assessment measures the same thing in different populations. There are reasons to believe that measurement invariance of the Wechsler scales may not hold for people with an intellectual disability. Many of the issues which may influence factorial invariance are common to all versions of the scales. The present study, therefore, explored the factorial validity of the WAIS-III as used with people with an intellectual disability. Confirmatory factor analysis was used to assess goodness of fit of the proposed four factor model using 13 and 11 subtests. None of the indices used suggested a good fit for the model, indicating a lack of factorial validity and suggesting a lack of measurement invariance of the assessment with people with an intellectual disability. Several explanations for this and implications for other intellectual assessments were discussed.     

Psychometric qualities of a tetrad WAIS-III short form for use in individuals with mild to borderline intellectual disability

Objective: To investigate the reliability and validity of a Wechsler Abbreviated Scale of Intelligence-based Wechsler Adult Intelligence Scale – third edition (WAIS-III) short form (SF) in a sample of individuals with mild to borderline intellectual disability (MBID) (N?=?117; M_IQ?=?71.34; SD_IQ?=?8.00, range: 52–85). Methods: A full WAIS-III was administered as a standard procedure in the diagnostic process. Results: The results indicate an excellent reliability (r?=?0.96) and a strong, positive correlation with the full WAIS-III (r?=?0.89). The SF correctly identified ID in general and the correct IQ category more specifically in the majority of cases (97.4% and 86.3% of cases, respectively). In addition, 82.1% of the full scale IQ (FSIQ) estimates fell within the 95% confidence interval of the original score. Conclusions: We conclude that the SF is a reliable and valid measure to estimate FSIQ. It can be used in clinical and research settings when global estimates of intelligence are sufficient.     

Estimating the level of functional ability of children identified as likely to have an intellectual disability

Screening tools can provide an indication of whether a child may have an intellectual disability (ID). Item response theory (IRT) analyses can be used to assess whether the statistical properties of the tools are such that their utility extends beyond their use as a screen for ID. We used non-parametric IRT scaling analyses to investigate whether the Child and Adolescent Intellectual Disability Screening Questionnaire (CAIDS-Q) possessed the statistical properties that would suggest its use could be extended to estimate levels of functional ability and to estimate which (if any) features associated with intellectual impairment are consistently indicative of lower or higher levels of functional ability. The validity of the two proposed applications was assessed by evaluating whether the CAIDS-Q conformed to the properties of the Monotone Homogeneity Model (MHM), characterised by uni-dimensionality, local independence and latent monotonicity and the Double Monotone Model (DMM), characterised by the assumptions of the MHM and, in addition, of non-intersecting item response functions. We analysed these models using CAIDS-Q data from 319 people referred to child clinical services. Of these, 148 had a diagnosis of ID. The CAIDS-Q was found to conform to the properties of the MHM but not the DMM. In practice, this means that the CAIDS-Q total scores can be used to quickly estimate the level of a person's functional ability. However, items of the CAIDS-Q did not show invariant item ordering, precluding the use of individual items in isolation as accurate indices of a person's level of functional ability.     

Reliability and validity of the SPAID-G checklist for detecting psychiatric disorders in adults with intellectual disability

SPAID (Psychiatric Instrument for the Intellectually Disabled Adult) is the first Italian tool-package for carrying out psychiatric diagnosis in adults with Intellectual Disabilities (ID). It includes the “G” form, for general diagnostic orientation, and specific checklists for all groups of syndromes stated by the available classification systems. SPAID was established to provide an easy and quick tool for daily practice of the personnel working with ID. The present study was aimed at evaluating psychometric and psychodiagnostic characteristics of the SPAID-G and at supplying new data on the prevalence rate of psychiatric disorders in a multicentric Italian sample of people with ID living in different settings. The SPAID-G was randomly applied to 304 participants with ID attending residential facilities or assessment services across Italy. A part of the sample was also consecutively assessed through the use of DASH, PDD-MRS and by the clinical application of the DSM-IV TR criteria. The correlation between SPAID-G scores and those provided by other evaluation tools was over 60%. Additionally, the internal consistency and inter-rater reliability resulted to be good. Psychopathological symptoms were detected in approximately 40% of the sample. Respectively, autistic spectrum disorders, impulse control disorders, mood disorders, and dramatic personality disorders were the diagnostic orientations providing the most prevalent over-threshold scores. SPAID-G seems to be a valid diagnostic tool, quick and easy to use in psychiatric disorders assessment within the Italian population with ID.     

Differences in the intellectual profile of children with intellectual vs. learning disability

The WISC-IV was used to compare the intellectual profile of two groups of children, one with specific learning disorders (SLDs), the other with intellectual disabilities (ID), with a view to identifying which of the four main factor indexes and two additional indexes can distinguish between the groups. We collected information on WISC-IV scores for 267 children (M_age = 10.61 [SD = 2.51], range 6–16 years, females = 99) with a diagnosis of either SLD or ID. Children with SLD performed better than those with ID in all measures. Only the SLD children, not the ID children, revealed significant differences in the four main factor indexes, and their scores for the additional General Ability Index (GAI) were higher than for the Cognitive Proficiency Index (CPI). Children with a diagnosis of SLD whose Full-Scale Intelligence Quotient (FSIQ) was <85 showed a similar pattern. Our findings confirm the hypothesis that children with SLD generally obtain high GAI scores, but have specific deficiencies relating to working memory and processing speed, whereas children with ID have a general intellectual impairment. These findings have important diagnostic and clinical implications and should be considered when making diagnostic decisions in borderline cognitive cases.     

Epilepsy in children with intellectual disability in Bosnia and Herzegovina: Effects of sex, level and etiology of intellectual disability

The purpose of this study was to examine the occurrence of epilepsy in children with intellectual disability. An additional goal was to determine if there were statistical differences in the occurrence of epilepsy related to the sex, level and etiology of intellectual disability of children. The sample consisted of 167 children with intellectual disability attending two special education schools in Sarajevo, Bosnia and Herzegovina. The method for data collection was the examination of the children's medical records. A chi-square test was performed to determine if there were any significant differences in the occurrence of epilepsy among different categories of children with intellectual disability. Additionally, Phi coefficient and Cramer V coefficient were calculated to determine the strength of association. The occurrence of epilepsy in children with intellectual disability is high and certain etiological categories are associated with an even higher risk of epilepsy.The study confirmed a high occurrence of epilepsy in children with intellectual disability. Some psycho-educational implications of epilepsy were discussed and in the future there should be better cooperation between medical and educational institutions in treating the bio-psycho-social issues of a child with epilepsy.     

Effects of exercise on physical fitness in children with intellectual disability

This paper presents the results of the study which examined the effects of carefully designed physical exercise programs on the development of physical fitness in children with ID. The study sample consisted of 42 children with ID and 45 typically developing children. All the participants were assessed using Eurofit Test Battery. The results were analyzed in terms of participation in the exercise program and level of intellectual functioning. While ID children scored significantly lower on fitness tests when compared with typically developing children, the study revealed an association between degree of ID and physical fitness.     

Rates of breastfeeding and exposure to socio-economic adversity amongst children with intellectual disability

Children with intellectual disability are at increased risk of experiencing poor health relative to their typically developing peers. Previous research indicates that exposure to socio-economic disadvantage contributes towards this disparity but that additional factors (including parenting practices) may be involved in mediating/moderating pathways. This study examined duration of breastfeeding amongst children with and without intellectual disability by a secondary analysis of data from the UK Millennium Cohort Study. Children with intellectual disability were significantly less likely to have been ever breastfed; breastfed exclusively or at all at 3 months or breastfed at all at 6 months relative to children without intellectual disability. None of these differences remained significant when other psycho-social risk factors for reduced breastfeeding were controlled for. The study adds to both the sparse literature on breastfeeding practices amongst families of children with intellectual disability and research demonstrating relationships between socio-economic disadvantage and wellbeing for children with intellectual disability.     

An evaluation of social and adaptive skills in adults with bipolar disorder and severe/profound intellectual disability

The purpose of this study was to explore the interrelationship of social and adaptive skills in adults with bipolar disorder and severe or profound intellectual disability. A bipolar group (N=14), a severe psychopathology group without bipolar disorder (N=14), and a control group with no DSM-IV Axis I diagnosis (N=14) were compared on the Vineland Adaptive Behavior Scale (VABS) and the Matson Evaluation of Social Skills for Individuals with sEvere Retardation (MESSIER). Bipolar patients had significantly more negative verbal social skills than the other two groups on the MESSIER, but no group differences on the VABS were noted. The implications of these data are discussed for a better understanding of bipolar disorder in persons with intellectual disability.     

Analysis of seasonal influenza vaccine uptake among children and adolescents with an intellectual disability

The aim of the present study was to describe the seasonal influenza vaccination rate and to examine its determinants for children and adolescents with intellectual disabilities (ID) living in the community. A cross-sectional survey was conducted to analyze the data on seasonal influenza vaccination rate among 1055 ID individuals between the ages of 12-18 years. The results found that 22.9% of the study participants used the vaccine during the past three years, and the vaccination rate among different age groups varied from 18.1 to 26.5%. There was no gender difference of seasonal influenza vaccination rate among age groups. Multilevel logistic regression analysis revealed that ID individuals with moderate (OR = 1.59, 95% CI = 1.08-2.34) or severe (OR = 2.31, 95% CI = 1.20-4.45) disability, with an illness (OR = 1.64, 95% CI = 1.02-2.63), who have general health exams (ever used, OR = 1.57, 95% CI = 1.03-2.40; regularly used, OR = 1.89, 95% CI = 1.05-3.41) were more likely to have seasonal influenza vaccination than their counterparts. The present study highlights that the substantial disparity in receipt of seasonal influenza vaccine in children and adolescents with ID reflects the effects of disability level, disease condition, and general health exam experience and suggests the need for greater attention to factors affecting ID individuals to improve their preventive health care.     

Self-regulation and performance in problem-solving using physical materials or computers in children with intellectual disability

This study compares self-regulation in 29 children with intellectual disability and 30 typically developing children, who solved tasks using physical materials or computers. Their cognitive, linguistic levels were assessed in order to match the children of both groups. In the presence of their mothers and fathers, the children were asked to perform eight tasks presented using two types of medium (physical materials and computer). Performance and task completion time were recorded. Seven self-regulated strategies were analyzed: identification of objective, planning, self-attention, self-motivation, joint attention, behaviour regulation and self-evaluation. Children in the two groups did not differ in their self-regulation, and in each group, their chronological age had no significant effect on their self-regulation. However, whatever the medium used, their mental age had a significant effect on their overall self-regulation and on six self-regulated strategies: identification of objective, planning, self-attention, self-motivation, behaviour regulation, and self-evaluation. A positive link between overall self-regulation and language abilities was only obtained in the group of typical developers. In addition, although no significant effect of the medium on overall self-regulation was observed in each group, an effect of the type of medium was obtained concerning three specific self-regulated strategies, though not in the same direction: self-attention and self-evaluation are better with the computer than with physical materials, whereas joint attention is better with physical materials than with the computer. In both groups, overall self-regulation, whatever the medium, correlated positively and highly significantly with performance in different tasks (but not with completion time). In each group, variable correlational patterns were obtained between specific self-regulated strategies and performance in each task with each medium: inter-task variability of efficiency of distinct strategies was observed.     

The antecedents of loneliness in older people with an intellectual disability

IntroductionThe cognitive discrepancy approach to loneliness is often used to describe loneliness in ageing populations, but to date, it has never been used to explore loneliness in older people with an intellectual disability. An analysis is needed utilising a refined list of causes of loneliness in this population.MethodUsing data from a nationally representative dataset of people aged over 40 with an intellectual disability (N = 708), this analysis runs repeated regressions of variables grouped into conceptual blocks, organised from sociodemographic to network quality.ResultsVariables selected predicted 23% of the loneliness variance. Functional limitations, education, working in the community, transport difficulties, pain, stress caused by service change, emotional health problems and confiding were all significant predictors of loneliness.ConclusionThat for those with fewer functional limitations only transport difficulties precipitated loneliness, suggests living a more independent life protects from loneliness, in this group. Those with functional limitations and who lead a more service dependent life appear more exposed to loneliness precipitating variables.     

Characteristics influencing attendance at a primary care health check for people with intellectual disability: An individual participant data meta-analysis

BackgroundHealth checks benefit adolescents and adults with intellectual disability, however uptake is low despite government–funded incentives.AimTo assess the characteristics of people with intellectual disability who, when offered a health check with their primary care physician at no cost, completed the health check.Methods and proceduresData from three randomised controlled trials considering health checks in people with intellectual disability living in the community were included in an individual-patient data meta-analysis. The studies used the same health check and the participant characteristics investigated (age, sex, cause of disability, level of disability and socio-economic position) were defined identically, but participants were sourced from different settings: adults living in 24-h supported accommodation, adults living in private dwellings, and school-attending adolescents.Outcomes and resultsIn total 715 participants were offered health checks. Compared to participants with Down syndrome, participants with other known causes of disability were more likely not to attend their health check (odds ratio;95%CI) = (2.5;1.4–4.7), as were participants with no known cause of disability (2.3;1.2–4.3). These associations remained significant after adjusting for potentially confounding variables.Conclusion and implicationDown syndrome was the only characteristic positively associated with health check attendance across all study settings. Future research should focus on strategies to increase health check uptake in this population.     

The intellectual disability version of the very short form of the physical self-inventory (PSI-VS-ID): cross-validation and measurement invariance across gender, weight, age and intellectual disability level

Recently Maïano, Bégarie, Morin, and Ninot (2009) developed and validated an intellectual disability (ID) version of the very short form of the physical self-inventory (PSI-VS-ID). In a recent review of the various physical self-concept instruments Marsh and Cheng (in press) noted that the short and very short versions of the French PSI represent an important contribution to applied research but that further research was needed to investigate the robustness of their psychometric properties in new and diversified samples. Thus, this study is specifically designed to investigate the robustness of the PSI-VS-ID psychometric properties in a new independent sample of 248 adolescents and young adults with ID. In particular, tests of measurement invariance were conducted across the present sample and the original sample from Maïano et al. (2009) study in order to more precisely assess the degree of replication of the results. Overall, results from a series of confirmatory factor analyses of the PSI-VS-ID provided support for its: (i) factorial validity and reliability; (ii) factorial invariance across gender and weight status; (iii) partial (strict or strong) factorial invariance across age, ID level and samples; and (iv) latent mean differences across gender, weight status and ID level groups.     

Stress and residential staff who work with people who have an intellectual disability: a factor analytic study

The present study describes the development of a questionnaire, and the subsequent collection of data, to gather information on the demands and supports which influence stress (as measured by anxiety and depression scales) in direct care staff who work with people with intellectual disability. The results from the questionnaire were also used to explore the relationships between the factors derived from the questionnaire and to consider how these may be influential in building organizational models. The questionnaire was specifically constructed to measure the demands and supports experienced by direct care staff. The participants included 216 staff working in community residential services for people with intellectual disability. These individuals included staff working for two British health trusts and similar staff working for one local authority. The questionnaire consisted of 33 demands items and 23 supports items. Separate factor analyses were conducted on the demands and supports scales. Analyses of the reliability and validity of the resulting factors were conducted. Stepwise multiple regressions were conducted to further explore the relationship of factors with the measures of anxiety and depression. Four factors were extracted from the demands scale and three factors from the support scale. There was some concern over levels of reliability and validity for individual factors; however, the reliability of the main scales appeared to be satisfactory. All but one support factor correlated significantly with levels of anxiety and depression. The factors explained a modest amount of the variance in the regressions. While there are some concerns about the psychometric properties of the questionnaire, it is argued that the scales and factors can be used to confirm and further understanding of the relationship between groups of demands, supports and stress in staff. The usefulness of the questionnaire as a means of diagnosing specific sources of demand and support is considered. It is suggested that the questionnaire could form the basis for assessment and subsequent intervention in houses where staff are reporting relatively high levels of anxiety and depression.     

Reliability and responsiveness of the Bruininks–Oseretsky Test of Motor Proficiency-Second Edition in children with intellectual disability

We examined the internal consistency, test–retest reliability, and the responsiveness of the Bruininks–Oseretsky Test of Motor Proficiency-Second Edition (BOT-2) for children with intellectual disabilities (ID). One hundred children with ID aged 4–12 years tested on 3 separate occasions: two baseline measurements with a 2-week interval before the intervention, and a follow-up measurement after 4 months of pediatric rehabilitation program. The test–retest reliability and internal consistency of the total scale were excellent, with an ICC of 0.99 (95% confidence interval) and α of 0.92. Responsiveness was acceptable for all BOT-2 measures except the balance subtest. The minimal detectable change (MDC) and the minimal important difference (MID) values yielded a lower sensitivity level but a higher specificity level. Implications for interpreting these responsiveness indices are discussed.     

New model of mapping difficulties in solving analogical problems among adolescents and adults with intellectual disability

The main goal of the study was to map the difficulties and cognitive processes among adolescents (aged 13-21, N = 30) and adults (aged 25-66, N = 30) with mild and moderate intellectual disability (ID) when solving analogical problems. The participants were administered the Conceptual and Perceptual Analogical Modifiability test. A three-fold tailored dynamic assessment (DA) model for mapping difficulties was constructed based on Sternberg's analogical components model (encoding, inference, mapping, application): (a) mapping pre-teaching difficulties; (b) assessing the level of mediation; and (c) analyzing post-teaching responses. Another goal was to find out whether participants receiving “tailored” mediation would receive higher scores than participants receiving the standard DA procedure (adolescents aged 14-20; N = 30) and adults (25-55, N = 31). Repeated measures MANOVA of time × age × ID level indicated significant pre to post-teaching improvement across all age groups and ID levels. The adults gained more from mediation than the adolescents. The tailored DA model was more effective in producing change than the standard DA model. The greatest difficulties in the pre-teaching stage were in inference and mapping of perceptual analogies, where the participants received the highest level of mediation. Stepwise regression analysis indicated that inference, ID level and age predicted modifiability in the application of conceptual analogies, whereas encoding, ID level and mediation for inference predicted modifiability in the application of perceptual analogies.     

Providing services in the United Kingdom to people with an intellectual disability who present behaviour which challenges: a review of the literature

There is ongoing debate about the best model of service provision for people with an intellectual disability who present severe behavioural challenges. The present paper reviewed research which evaluated a range of UK service provision in terms of impact on challenging behaviour and other quality of life indices. A literature search was carried out for English language papers from 1990 to 2010 using a range of databases. Secondary searches were carried out from references of relevant papers. Very few evaluations were found. The available research indicates that, on the whole, specialist congregate services for individuals with challenging behaviour appear to use more restrictive approaches which have limited effect on reducing challenging behaviour. The evidence for peripatetic teams is somewhat unclear. The two studies reviewed showed positive outcomes, but both had limitations that made it difficult to generalize the results. A similar limitation was found with the sole evaluation of a community based service. It is unlikely that one model of service provision will meet the needs of all individuals, however, more robust evaluations are required of existing service models to allow commissioners, service users, their families and carers to make fully informed choices about effective services for those who challenge.