A psychometric evaluation of dementia rating scales

The paper discusses the relevance of sufficient psychometric standards for dementia rating scales. The concurrent, convergent and construct validity of the Mini Mental State Examination (MMSE), the Alzheimer's Disease Assessment Scale (ADAS) and the CAMCOG are assessed. The Clinical Global Impressions and the Global Deterioration Scale are used as global scales. The concurrent and convergent validity are satisfactory. The construct validity expressed by the Cronbach and Loevinger coefficient are very good for all scales and subscales. The Mokken's single item coefficients show that the MMSE has the best individual hierarchical fit, the item reading can be left out. The ADAS is less uni-dimensional, eight items can be left out. The CAMCOG consists of too many items to apply the Mokken's single item coefficients or the Loevinger coefficient. Instead, the CAMCOG subscales are analyzed. This results in a possible reduction of the CAMCOG by 30 items to a total of 35 items. The factor analysis reveals two factors in both the MMSE and the ADAS while the number of observations does not allow a factor analysis of the CAMCOG to be performed.