«Faculty for People with Intellectual Disabilities Dementia and People with Intellectual Disabilities Guidance on the assessment, diagnosis, ...»
There are a wide variety of tools utilised in the UK to assess dementia in people with intellectual disabilities. A systematic review (Zeilinger et al., 2013) found some measures currently used in the UK were neither designed for the assessment of dementia, nor for people with intellectual disabilities. There is currently no agreed battery of assessments with which to assess dementia in this population and there is often great variation in screening/assessment methods. There continues to be a lack of research data to secure agreement in order for there to be better uniformity across services and for future data to be pooled and compared. Lack of research data and the nature of the intellectual disability population requires each individual to be viewed independently in terms of their own functioning. Cognitive and informant-based assessments serve as a unique baseline to that individual.
Colleagues in the US (National Task Group on Intellectual Disabilities and Dementia I Practices (NTG), Moran et al., 2013) have recently developed practice guidelines that helpfully describe the key stages of a dementia evaluation in this population and has published an Early Detection Screening Tool (NTG-Early Detection Screen for Dementia).
Always look for evidence from previous assessments on file that might indicate preI morbid functioning. Where possible, the same test should then be repeated for comparison.
The tests used should include (where possible) direct assessment with the person and I questionnaire/interview-based assessments with well-informed carers. Information should be collected from both carers at home and from carers within the person’s day services to ensure concerns are not situation-specific.
For some individuals with profound intellectual disabilities, pre-morbid cognitive I ability may be so poor that changes may not be detected by any available standardised testing. Carer reports have to take precedence.
Whatever battery of assessments is chosen, it should be used longitudinally within the I service to enable comparison of performance over time for that individual.
6.3 Direct testing with the person with Down’s syndrome/ intellectual disabilities It is well recognised that the early changes associated with dementia in people with Down’s syndrome can often relate to behaviour or personality rather than memory functioning (Oliver et al., 2011; Adams & Oliver, 2010; Ball et al., 2006b, 2008, 2010). These studies suggest that there is often compromised function associated with the frontal lobes early in the course of the disease. For this reason, assessments that tap into executive functioning are important to consider, especially in terms of establishing baselines when a person is still healthy and well.
Guidance on their Assessment, Diagnosis, Interventions and Support 27 Assessments should cover as a minimum (although may be dependent on intellectual
functioning and ability to engage in direct assessment):
• a validated instrument for the cognitive assessment of dementia in people with intellectual disabilities (see ‘Neuropsychological Assessments and Informant Questionnaires’ sections below for examples);
• prospective, short- and long-term memory (visual and verbal);
• executive functioning;
• language (expressive and comprehension); and
• recording of evidence of new learning.
Other assessment to consider:
• Mood state.
• Examples of reading/writing/mathematic skills can support a helpful baseline to ascertain changes to these skills over time. Examples/references to these skills can often be found in historic files.
• Direct questioning of known previous skills or knowledge personal to the individual (e.g. order of potting balls in snooker, knowledge about a favourite entertainer.) This is not a complete list and the assessor need to be responsive to assessing specific issues in greater detail if required (e.g. praxis, attention, perception).The tools listed below are those most commonly used in services in the UK. Many services have developed their own ‘assessment battery’ combining a variety of psychometric measures and assessments that tap into the areas of functioning described above. Specific recommendations cannot be made until there is more research evidence comparing their efficacy.
6.3.1 Direct neuropsychological assessment Neuropsychological Assessment of Dementia in Adults with Intellectual Disabilities (NAID) (Crayton et al., 1998). The NAID is a battery of very simple tests covering memory, orientation, language and praxis. There is no manual, rather the instructions are in Crayton et al. (1998) and data in Adams and Oliver (2006). This battery takes about 45 minutes to administer. The majority of people with Down’s syndrome can attempt most of it. It is said by the authors to be in use in over 30 intellectual disabilities services in the UK.
CAMCOG-DS is the neuropsychological assessment part of the CAMDEX-DS (Ball et al., 2006). It is a concise neuropsychological test battery which is based on the CAMCOG, which was designed to meet the need to assess all the cognitive deficits specified in criteria for dementia, i.e. memory impairment, aphasia, apraxia, agnosia and disturbance in thinking (executive function). The CAMCOG-DS includes assessments of orientation, language, memory, attention, praxis,
thinking and perception, giving individual subscale scores as well as a total score.
Severe Impairment Battery (SIB) (Saxton et al., 1993). The SIB is designed to assess cognitive abilities at the lower end of the intellectual range in the general population (age range 51–91). There are 40 items and administration is said to take about 20 minutes. It is composed of very simple one-step commands which are presented in conjunction with gestural cues (e.g. ‘what’s your name?’, ‘please write your name here’, ‘what do you call the thing you drink coffee from?’). The SIB is divided into scoreable subscales, each sampling 28 Dementia and People with Intellectual Disabilities within the range expected of the severely-impaired individual. The six major subscales are attention, orientation, language, memory, visuospatial ability and construction. There are also brief evaluations of praxis and the person’s ability to respond appropriately when his/her name is called (orienting to name). In addition, there is an assessment of social interaction skills. It yields scores out of 100, to assess mild to moderate dementia. There is no cut-off for ‘normal’ as the test should only be used with people known to be severely impaired.
Test for Severe Impairment (Albert & Cohen, 1992). This is a 24-item test covering eight domains which was designed for people with severe cognitive dysfunction, but not specifically intellectual disabilities. This test may not be sensitive to change over time, and only includes a few memory items.
Tests of executive functioning Whilst there have been some recent studies exploring the measurement of executive functioning in people with intellectual disabilities (e.g. Ball et al., 2009) there is currently no clear agreement as to which tests should be adopted for the assessment of dementia.
Individual assessments such as tests of verbal/category fluency, response inhibition tests such as the Cats and Dogs Test or scramble boxes (see Ball et al., 2008 for descriptions), and set/rule switching tasks such as card sorting tests (Weigl sorting; Dimensional Change Card Sort test) are sometimes used as a part of wider bespoke test batteries to establish functioning in these areas. This is helpful when setting a baseline of functioning that may be used for future comparison.
Executive test batteries developed for the non-intellectual disabilities population (such as the Delis-Kaplan Executive Function System – D-KEFS (Delis et al., 2001) or the Behavioural Assessment of the Dysexecutive Syndrome – BADS (Wilson et al., 1996) tend to be too difficult for many people with intellectual disabilities, although some sub-tests (e.g. key search) may be used successfully in people with mild intellectual disabilities.
The BADS–ID (Webb & Dodd, 2014) is under development and may assist in filling the current gap in relation to suitable tests of executive functioning in people with intellectual disabilities.
The Measure of Everyday Planning (MEP) is a tool under development (Webb et al., 2014) and is a flexible tool designed to help identify the issues underlying difficulties that adults with intellectual disabilities may have with independently initiating, planning and carrying out everyday activities. It explores subtle factors that can impair the performance of individuals who, superficially, appear to have the ability to carry out tasks but, in reality, struggle with them.
The informant/carer versions of the DEX (found in the BADS, Wilson et al., 1996) and the Behaviour Rating Inventory of Executive Function – Adult Version – BRIEF–A (Roth et al.,
2000) may be useful in ascertaining areas of deficit in relation to executive functioning.
These can be used and baseline and repeated at intervals, or when concerns are raised to monitor changes in symptoms common to those with executive dysfunction.
Guidance on their Assessment, Diagnosis, Interventions and Support 29
6.4 Informant questionnaires These should aim to cover those areas of function that are known to deteriorate with the development of dementia including: short and long term memory, general mental functioning, dyspraxia and dysphasia, daily living skills and personality and behaviour.
Dementia Questionnaire for People with Learning Disabilities – DLD – formerly known as the DMR (Evenhuis et al., 2007). The DMR and its recent successor, the DLD, is widely used to longitudinally assess the development of dementia in adults with intellectual disabilities in the UK and Europe. It is a screening tool for the early detection of dementia in adults with intellectual disabilities, completed by carers, consisting of 50 items. There are eight sub-scales: short term memory, long term memory, orientation (making up Sum of Cognitive Scores), speech, practical skills, mood, activity and interest and behavioural disturbance (making up Sum of Social Scores). Evenhuis (1992) reported that the DMR had sensitivity of up to 100 per cent in identifying dementia and suggested change scores and cut-off scores that might be indicative of dementia. Prasher (1997) conducted an independent evaluation of the DMR on 100 adults with Down’s syndrome in the UK and, finding poor specificity, suggested modifications to the cut-off scores. A prospective 14-year longitudinal study (McCarron et al., 2014) stated the DMR/DLD to be the most sensitive tool in their battery for tracking change in symptoms over time.
The Dementia Scale for Down Syndrome – DSDS (Gedye, 1995). This is designed for use with people with Down’s syndrome but may also be useful for people with intellectual disabilities generally according to NICE (2006). It gives a measure of early, middle and late stages of dementia and includes the time course of the deterioration and a differential diagnosis scale. The psychometric property of the DSDS has never been published in a peer-reviewed journal. Its administration is restricted to clinical and other qualified psychologists and trained psychometricians.
Dementia Screening Questionnaire for Individuals with Intellectual Disabilities – DSQIID (Deb et al., 2007). The DSQUIID is designed to be ‘a user-friendly observer-rated dementia screening questionnaire with strong psychometric properties for adults with intellectual disabilities’, according to the authors. It comprises 43 questions in three sections. The scoring system overcomes the floor effect found in some other assessments.
Adaptive Behaviour Dementia Questionnaire – ABDQ (Prasher et al., 2004). This is a 15item questionnaire derived from the AAMD Adaptive Behavior Scale (Nihira et al., 1974) which is used to detect change in adaptive behaviour. It has been developed to screen specifically for dementia in Alzheimer’s disease in people with Down’s syndrome. It sets out to collect information on how the person compares now to their previous normal level of social functioning. It gives criteria for the presence of Alzheimer’s disease and a rating of severity, but the threshold scores may require revision as these do not appear to be accurate in clinical practice.
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6.5 Measures of psychological issues 6.5.1 Measures of mental health The PAS-ADD Checklist (Moss, 2002a) is a 25-item questionnaire designed for use primarily by care staff and families to help them decide whether further assessment of an individual’s mental health may be helpful. The scoring system includes threshold scores which, if exceeded, indicate the presence of a potential psychiatric problem, which may then be more fully assessed using the Mini PAS–ADD. The PAS–ADD Checklist produces three scores, relating to affective or neurotic disorder; possible organic condition (including dementia); and psychotic disorder.
The Mini-PAS-ADD Interview (Moss, 2002b) is designed to provide highly reliable information on psychiatric symptoms, usually by informant interview. The assessment produces scores relating to seven diagnostic categories: Depression; Anxiety; Expansive mood; Obsessive compulsive disorder; Psychosis; Unspecified disorder (mostly dementia and other organic problems in our field-trial sample); and Autistic spectrum disorder.
Threshold scores are provided for each of the above seven diagnostic areas. If the person reaches or exceeds a threshold, the implication is that they probably warrant a diagnosis.
However, a strong emphasis is placed on clinical interpretation of the results.
6.5.2 Measures of depression The Glasgow Depression Scale (client version) – GDS-LD (Cuthill et al., 2003). A 20-item questionnaire designed for use with people with intellectual disabilities. It has a three point Likert-type response scale (‘never’, ‘sometimes’, ‘a lot’). It has a suggested cut-off score for suspected depressive illness.