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.