Bedside cognitive screening instruments. A critical assessment.
Bedside cognitive screening instruments are used increasingly in clinical and research settings to detect cognitive impairment and to quantify its severity. The authors review the five most frequently cited bedside screening tests that use an interview format and require brief administration times: the Mini-Mental State Examination, the Cognitive Capacity Screening Examination, Mattis Dementia Rating Scale, Kahn's Mental Status Questionnaire, and the Short Portable Mental Status Questionnaire. The tests all have adequate inter-rater reliability, and adequate test-retest reliability has been established for three of the tests. All of the tests show close correspondence with clinical diagnoses of delirium and dementia and are useful for the diagnosis and quantification of these syndromes. However, there is currently no evidence that the tests increase the level of diagnostic accuracy achieved through clinical examination alone. All of the tests have substantial false-negative rates, with false-negative errors frequent among patients with focal lesions, particularly of the right hemisphere. False-positive errors may be more common among patients with less education and lower socioeconomic status. The tests reviewed do not detect many types of cognitive deficit that may bear critically on differential diagnosis and case management. Suggestions are given for further research on the current measures and for the development of new screening tests that would meet a broader range of clinical purposes.