The validation of a mailed health survey for screening of dementia of the Alzheimer's type

OBJECTIVE: To test the efficacy of a mailed health survey, which included the Clock Completion Test (CCT), to screen previously undiagnosed older adults for dementia of the Alzheimer's type (DAT) in a community-dwelling population, and to determine whether the addition of selected risk factors for Alzheimer's disease (AD) would enhance the screening instrument's operating characteristics. DESIGN: Comparison of the results of a self-administered screen for DAT with the diagnosis of DAT by clinician evaluation or telephone interviews. SETTING: A geriatric assessment clinic. PARTICIPANTS: Three hundred and five women age 65 and older from St. Louis, Missouri. MEASUREMENTS: The sensitivity and specificity of the CCT and the CCT plus risk factors for AD were evaluated using two standards: The Short Blessed Test (SBT) and the physician diagnosis of probable AD using National Institute of Neurological and Communicative Disorders and Stroke - Alzheimer's Disease and Related Disorders Association criteria. RESULTS: Sensitivity and specificity for the CCT by SBT criteria were 63% and 79%, respectively. Using the physician's assessment as a criterion, the CCT had better sensitivity (67%) but poorer specificity (69%). Adding two or more risk factors for AD improved sensitivity and specificity to 71% and 89% and, in the physician assessment subgroup, to 75% and 87%, primarily by halving the false-positive rate. CONCLUSION: The combination of the simple, self-administered CCT and two or more AD risk factors is a more effective screening instrument for DAT and potentially preclinical DAT than the CCT alone. However, the instrument may be better suited for use in an office setting because of a poor response rate by subjects with dementia.