Review: some screening tests for dementia are accurate and practical for use in primary care
Correspondence to: Dr T Holsinger, Durham VA Medical Center, Durham, NC, USA;
How accurate are screening tests for detecting dementia in older people in primary care settings?
MEDLINE and PsycINFO (2000 to April 2006). Earlier studies were covered by a previously published review.*
Study selection and assessment:
English-language studies that evaluated screening tests for dementia used by general practitioners in people >60 years of age who did not have clinically obvious dementia. Included studies were required to use an acceptable criterion standard to diagnose dementia. Studies of patients in institutions or with <6 years of education, and those involving diagnostic imaging or laboratory or physiological tests were excluded. 29 studies involving 38 assessments of 25 screening instruments met the selection criteria. Quality of individual studies was assessed based on sample size, participant selection, and use of a credible reference standard applied blindly and independently.
positive (+LR) and negative (−LR) likelihood ratios.
Meta-analysis was not done because of differences in tests evaluated and study designs. Results are summarised in the table. The Mini-Mental State Examination (MMSE), the standard screening instrument for dementia, takes 7–10 minutes to administer and had a median +LR of 6.3 and a median –LR of 0.19. Brief screening tests, such as the Memory Impairment Screen, Abbreviated Mental Test, clock drawing, 7-Minute Screen, and Short Cognitive Evaluation Battery, take 1–10 minutes, assess fewer domains, and were of variable usefulness for screening for dementia. More comprehensive instruments, such as Cambridge Cognitive Examination, Community Screening Interview for Dementia, and Modified MMSE, take 10–45 minutes and had a median +LR of 8.9 and a median –LR of 0.12. Instruments for special situations, such as screening by telephone (Memory Impairment Screen—Telephone Version and Telephone Interview for Cognitive Status), written questionnaires (Cognitive Assessment Screening Test), and use in highly educated patients (Hopkins Verbal Learning Test), were also useful for screening for dementia.
Screening tests to identify dementia in older people in primary care settings vary in diagnostic accuracy and administration time. No single instrument is ideal for all settings.
*Boustani M, Peterson B, Hanson L, et al. Ann Intern Med 2003;138:927–37.
A modified version of this abstract appears in ACP Journal Club.
Holsinger T, Deveau J, Boustani M, et al. Does this patient have dementia? JAMA 2007;297:2391–404.
Because a large proportion of community-dwelling older adults have undetected dementia,1there is a need to increase the use of appropriate dementia screening tools in primary care. The systematic review by Holsinger et al built on a previous review of the topic. The authors provided substantiated and clear recommendations that are consistent with best practice guidelines for nurses.2 However, this systematic review offers stronger evidence and further direction about the choice of tools that are appropriate for use with older adults in specific situations.
The fact that Holsinger et al were unable to conduct a meta-analysis because of the variability of thresholds for a positive screening result calls attention to the insidious and unpredictable nature of dementia, particularly in the early stages. The studies in this review were limited to those involving community-dwelling older adults, a restriction that is surprising given the high proportion of older adults with dementia who live in long-term care facilities. Older adults in long-term care are often labelled with a false-positive diagnosis of dementia because of a lack of appropriate screening and evaluation, often precluding effective treatment of the true underlying problem.
It is important for nurses to be able to distinguish dementia from other common states, such as delirium and depression, through the use of appropriate screening tools. Once dementia is suspected, a comprehensive assessment should be done to rule out other conditions (eg, pain, side effects of medications, and infection) that often mimic behavioural and cognitive responses consistent with dementia. Such a process will help to optimise function and reduce excess disability in this vulnerable population.