Cognitive screening and neuropsychological assessment in early Alzheimer'sdisease

Neuropsychological assessment provides a reliable means of detecting dement ia in its earliest stages and of tracking the progression of cognitive decl ine over time. In addition, patterns of cognitive deficits revealed with ne uropsychological testing can aid in the differential diagnosis of the vario us dementing disorders.(149) Until effective and easily obtainable biologic markers for detecting the onset and progression of AD are developed, neuro psychological assessment will continue to play an important role in the dem entia evaluation. Although the clinical research studies reviewed previously clearly illustra te the important contribution that neuropsychological testing can make to t he dementia evaluation, a number of factors must be considered when testing cognitive function in elderly individuals who may have AD. Performance on cognitive tests can be adversely affected by poor vision or hearing; impair ed or fluctuating consciousness (e.g., delirium); poor compliance because o f concomitant behavioral or psychiatric disorders; current or past substanc e abuse; and the use of certain medications. These factors must be consider ed and corrected, if possible, to ensure reliable and valid cognitive asses sment. Performance on most structured cognitive tests is also clearly influ enced by level of education and literacy, and these factors must be taken i nto consideration when selecting assessment measures and when interpreting test results. Although ethnicity and socioeconomic status do not seem to ha ve a particularly notable effect on performance after the effects of educat ion are accounted for, most cognitive measures do have cultural idiosyncras ies that must be considered when the test is adopted for use in a non-Engli sh-speaking population. Normative data that account for ethnicity are now a vailable for only a limited number of neuropsychological tests. The problem of educational and ethnicity biases in evaluation of suspected AD can also be ameliorated, to some extent, by repeated testing that allows decline fr om an individual's own baseline level of cognitive functioning to be observ ed.