Global assessment measures

The diagnosis of dementia is a clinical one, requiring the identification of not just cognitive impairment, but that it is sufficiently severe to interfere with social or occupational functioning. No single cut-point on a given test discriminates dementia from other causes of cognitive impairment. Even neuropathological hallmarks of dementing diseases - the traditional ‘gold standard’ in dementia diagnosis - do not reliably discriminate between those who would be diagnosed with dementia from those without cognitive impairment.1 Given that clinical judgment is essential in dementia, it is not surprising that clinical global assessment scales are used routinely both to diagnose and stage dementia, and in research settings, including drug trials where they can be outcome measures.2 Clinical global scales characterize dementia through multidimensional assessments of cognitive, functional and behavioural aspects of the disorder.3 Here we critically review some commonly used clinical scales, emphasizing the ones which are judgment based. We note that any comprehensive dementia evaluation will also include cognitive tests that operate relatively independently of clinical judgment, such as the Mini-Mental State Examination (MMSE)4 and the Alzheimer’s disease Assessment Scale cognitive section (ADAS-cog), 5 but such psychometric tests will not be the focus of this chapter.