De Cognitieve Screening Test (CST) getoetst aan het schaalmodel van Mokken

In 1991 kwam voor klinisch gebruik in de psychogeriatrie de Cognitieve Screening Test (CST) beschikbaar. De CST heeft twintig items en bevat oriëntatievragen, vragen naar bekende publieke personen (zoals de huidige koningin, haar voorgangster, de minister-president) en vragen naar feiten uit voorbije jaren (zoals de jaartallen van de twee wereldoorlogen).1 Voor toepassing in de klinische praktijk is het belangrijk dat de somscore over de items van de CST betekenisvolle uitspraken toelaat over een eigenschap van de respondenten, zoals in dit geval hun niveau van cognitief functioneren. Betekenisvol kan op minstens twee manieren worden opgevat, in de zin van betrouwbaarheid en validiteit. Om betrouwbaar individuele verschillen te kunnen vaststellen, is het van belang dat de testscore respondenten systematisch ordent op de gemeten eigenschap. 2 Validiteit heeft betrekking op het verband tussen de gemeten (latente) eigenschap en de resultaten van andere metingen of observaties in verwante domeinen

Progressive Decline of Semantic Memory with Preservation of Number Processing and Calculation

A 75-year-old man with seven years of formal education displayed a syndrome of progressive and severe lexical impairments to word comprehension and production (semantic dementia). While he lost the ability to recognize written arithmetical signs, he could still retrieve the arithmetical facts for addition and subtraction of all number combinations of 1 to 9 and 11 to 19, though his mastery of multiplication tables (2 to 9) was unreliable. Calculation procedures were intact. Over the course of 18 months the components of the calculation system dissolved selectively: arithmetical procedures and number reading were spared, despite increasing damage to the arithmetic fact store. He retained the ability to read the time on analogue clocks. Selective preservation of components of the calculation system in the context of severe language deficits and dementia, supports the independent status of numerical abilities. The dissociation between intact arithmetical procedures and impaired table fact retrieval was paralleled by a dissociation between preserved procedures of phonology and syntax of language and impaired retrieval of content words, suggesting that the core deficit was a degradation of the central semantic store of learned knowledge of both words and arithmetic table facts

Measurement of overall quality of life in nursing homes through self-report: the role of cognitive impairment

Measuring quality of life is a necessity for adequate interventions. This paper concerns the usefulness of six self-report measures for overall quality of life for nursing home residents with various levels of cognitive impairment. It was investigated which proportion of residents from four cognition groups could complete a scale, and internal consistency and construct validity of the scales were studied. Data collection took place in ten Dutch nursing homes (N = 227). The proportion of residents that could complete each scale varied. The Depression List could be administered most often to the cognitively most impaired group (43%; Mini Mental State Examination-scores 0–4). In the three cognition groups with MMSE-score >5, internal consistency of the Depression List, Geriatric Depression Scale and Negative Affect Scale was adequate in all three groups (alpha ≥.68). Intercorrelation was highest for the Philadelphia Geriatric Center Morale Scale, the Depression List, and the Geriatric Depression Scale (rho ≥.65). Nonetheless, self-report scales were not strongly correlated with two observational scales for depression, especially in cognitively severely impaired residents (rho ≤.30). In conclusion, it may not be possible to measure overall quality of life through self-report, and possibly also through observation, in many nursing home residents

Item response theory analysis of cognitive tests in people with dementia:a systematic review

BACKGROUND: Performance on psychometric tests is key to diagnosis and monitoring treatment of dementia. Results are often reported as a total score, but there is additional information in individual items of tests which vary in their difficulty and discriminatory value. Item difficulty refers to an ability level at which the probability of responding correctly is 50%. Discrimination is an index of how well an item can differentiate between patients of varying levels of severity. Item response theory (IRT) analysis can use this information to examine and refine measures of cognitive functioning. This systematic review aimed to identify all published literature which had applied IRT to instruments assessing global cognitive function in people with dementia. METHODS: A systematic review was carried out across Medline, Embase, PsychInfo and CINHAL articles. Search terms relating to IRT and dementia were combined to find all IRT analyses of global functioning scales of dementia. RESULTS: Of 384 articles identified four studies met inclusion criteria including a total of 2,920 people with dementia from six centers in two countries. These studies used three cognitive tests (MMSE, ADAS-Cog, BIMCT) and three IRT methods (Item Characteristic Curve analysis, Samejima’s graded response model, the 2-Parameter Model). Memory items were most difficult. Naming the date in the MMSE and memory items, specifically word recall, of the ADAS-cog were most discriminatory. CONCLUSIONS: Four published studies were identified which used IRT on global cognitive tests in people with dementia. This technique increased the interpretative power of the cognitive scales, and could be used to provide clinicians with key items from a larger test battery which would have high predictive value. There is need for further studies using IRT in a wider range of tests involving people with dementia of different etiology and severity