Screening for cognitive impairment: comparing the performance of four instruments in primary care.

OBJECTIVES: To determine whether brief cognitive screening tests perform as well as a longer screening test in diagnosis of cognitive impairment, no dementia (CIND) or dementia.
DESIGN: A cross-sectional comparison of cognitive screening tests to an independent criterion standard evaluation using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria. Performance of the cognitive screening tests for identifying dementia, and separately for identifying dementia or CIND, was characterized using sensitivity, specificity, likelihood ratios, and diagnostic odds ratios.
SETTING: Three Department of Veterans Affairs primary care clinics. PARTICIPANTS: Of 826 independently living veterans aged 65 and older without a prior diagnosis of dementia, 639 participated and 630 were assigned a research diagnosis. MEASUREMENTS: Screening tests included the modified Mini-Mental State Examination (3MS; average time to administer, 17 minutes) and three brief instruments: the Memory Impairment Screen (MIS; 4 minutes), the Mini-Cog (3 minutes), and a novel two-item functional memory screen (MF-2; 1.5 minutes).
RESULTS: Participants were aged 74.8 on average and were mostly white or black. They were mostly male (92.9%) and had been prescribed a mean of 7.7 medications for chronic conditions. The prevalence of dementia and CIND was 3.3% and 39.2%, respectively. Sensitivity and specificity for dementia were 86% and 79% for the 3MS, 76% and 73% for the Mini-Cog, 43% and 93% for the MIS, and 38% and 87% for the MF-2, respectively.
CONCLUSION: In individuals without a prior diagnosis of cognitive impairment, the prevalence of dementia was low, but the prevalence of CIND was high. The 3MS and Mini-Cog had reasonable performance characteristics for detecting dementia, but a definitive diagnosis requires additional evaluation.