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Cochrane Special Collections

Diagnosing dementia

18 September 2020
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Special Collection

This Special Collection was first published for World Alzheimer’s Day 2019. This 2020 update includes newer reviews on dementia diagnosis. 

Accurate diagnosis is the first step in managing someone with cognitive concerns. Early diagnosis of a cognitive syndrome, if present, can allow people to make sense of their symptoms, and can help people plan their future, while allowing access to treatments and support. Governments and policymakers have recognized the need for early, robust diagnosis of cognitive problems, and in many countries targeted cognitive screening of older adults is recommended. Given the importance of early diagnosis, screening would seem intuitively attractive, but implementation of such policies would result in questions about the feasibility of dementia screening regarding scale, accuracy of tests, and management of results.

Although there have been exciting developments around neuroimaging and other biomarkers for dementia,[1,2] diagnosing dementia is still based on clinical assessment.[3] At a basic level, the dementia assessment collates information from the person with symptoms and others who know them, and looks for evidence of decline in cognition and any effects on daily function. In practice, this assessment often occurs in stages, possibly starting with a clinician using brief pencil and paper tests, or questionnaires about symptoms, to assess certain cognitive functions. These short screening tests allow for a form of dementia triage that can inform the need for more detailed, specialist assessment.

There are many cognitive screening tests and questionnaires available, with little consensus on the most appropriate test to use in various situations.[4] As a result, there is substantial inconsistency in the choice of tests used. External factors can force a change in practice, e.g. copyright and training issues with the Mini-Mental State Examination, and the Montreal Cognitive Assessment may dissuade clinicians from using these previously popular tests.

The COVID-19 pandemic has disrupted many aspects of healthcare, including dementia services. It has changed how we assess and diagnose people with memory and thinking concerns, while clinical services have had to rapidly adapt to video and telephone-based consultations rather than traditional face-to-face assessment. The Cochrane Dementia and Cognitive Improvement Group are prioritizing the collation of evidence on this new way of working and are developing a suite of reviews on this topic, with reviews in progress for telephone and video-call based dementia screening and questionnaire-based screening.

This Cochrane Library Special Collection presents reviews focussing on cognitive screening tests and questionnaires, and aims to be useful for clinicians, researchers, guideline writers, and policymakers. Supporting materials developed for researchers and reviewers are also included. The group is currently undertaking a prioritization exercise for questions of greatest relevance to dementia care, including aspects related to COVID-19, and can be contacted at the Cochrane Dementia and Cognitive Improvement website, or through social media @CochraneDCIG (Twitter).

Cognitive screening tests

Mini‐Mental State Examination (MMSE) for the detection of dementia in clinically unevaluated people aged 65 and over in community and primary care populations

Dementia is a progressive global cognitive impairment syndrome. The Mini-Mental State Examination (MMSE) is a cognitive test that is commonly used as part of the evaluation for possible dementia. This review aims to determine the diagnostic accuracy of the MMSE at various cut points for dementia in people aged 65 years and over in community and primary care settings who have not undergone prior testing for dementia.

Mini‐Mental State Examination (MMSE) for the detection of Alzheimer's disease and other dementias in people with mild cognitive impairment (MCI)

Some people with mild cognitive impairment (MCI) progress to dementia, but others remain stable or recover full function. It is important to find good predictors of dementia in people with MCI. The MMSE is the best‐known and the most often used short screening tool for providing an overall measure of cognitive impairment in clinical and research settings. This review determines the diagnostic accuracy of the MMSE at various thresholds for detecting individuals with baseline MCI, who would  convert clinically to dementia.

Mini‐Cog for the diagnosis of Alzheimer's disease dementia and other dementias within a community setting

The diagnosis of Alzheimer's disease relies on tests to evaluate cognition and discriminate between individuals with and without dementia. The Mini‐Cog is a brief, cognitive screening test that is frequently used to evaluate cognition in older adults in various settings. This review aims to determine if the Mini‐Cog test can be recommended to screen for cognitive impairment in community settings.

Mini‐Cog for the diagnosis of Alzheimer’s disease dementia and other dementias within a primary care setting

The majority of individuals with dementia will first present for care and assessment in primary care settings. There is a need for brief dementia screening instruments to diagnose dementia accurately in these settings. The Mini‐Cog is a brief, cognitive screening test that is frequently used to evaluate cognition in older adults in various settings. This review determines the accuracy of the Mini‐Cog for diagnosing Alzheimer’s disease dementia and related dementias in a primary care setting.

Mini‐Cog for the detection of dementia within a secondary care setting

There is a high prevalence of cognitive disorders, including undiagnosed dementia in secondary care settings. The Mini‐Cog is a short cognitive test comprising three‐item recall and a clock‐drawing test that is used in secondary care settings. Short cognitive tests can be helpful in identifying those who require further specialist diagnostic assessment; however, there is a lack of consensus around the optimal tools to use in clinical practice. This review assesses the diagnostic accuracy of the Mini-Cog when used for detecting Alzheimer's disease dementia and other dementias in a hospital (secondary care) setting.

Montreal Cognitive Assessment for the diagnosis of Alzheimer’s disease and other dementias

Global prevalence of dementia is projected to increase, particularly in resource‐limited settings. Recent policy changes in Western countries to increase detection mandates a careful examination of the diagnostic accuracy of neuropsychological tests for dementia. This review aims to determine the diagnostic accuracy of the Montreal Cognitive Assessment (MoCA) at various thresholds for dementia and its subtypes.

Addenbrooke’s Cognitive Examination III (ACE‐III) and mini‐ACE for the detection of dementia and mild cognitive impairment

The Addenbrooke's Cognitive Examination III (ACE‐III), and the mini‐ACE are brief, bedside cognitive screens that have previously reported good sensitivity and specificity. The quality and quantity of this evidence has not, however, been robustly investigated. This review assesses the diagnostic test accuracy of the ACE‐III and mini‐ACE for the detection of dementia, dementia sub‐types, and mild cognitive impairment (MCI) at published thresholds in primary, secondary, and community care settings in patients presenting with, or at high risk of, cognitive decline.

Informant questionnaires

Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the diagnosis of dementia within community dwelling populations

A variety of tools exists for initial assessment of possible dementia, but there is no consensus on the optimal method. Instruments using collateral sources to assess change in cognitive function over time may be especially useful. The most commonly used informant dementia assessment is the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). This review aims to determine the diagnostic accuracy of the IQCODE, for detection of all cause dementia in community‐dwelling adults without previous cognitive assessment.

Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the diagnosis of dementia within a general practice (primary care) setting

The IQCODE is a questionnaire, completed by a suitable 'informant' who knows the patient well, and is used as a tool to identify those who may have dementia. Brief tools that can be used for dementia "screening" or "triage" can be especially useful in primary care healthcare settings, but only if they are suitably accurate. This review describes the accuracy of IQCODE conducted in a primary care setting, against a clinical diagnosis of dementia.

Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE) for the diagnosis of dementia within a secondary care setting

The IQCODE is a questionnaire, completed by a suitable 'informant' who knows the patient well, and is used as a tool to identify those who may have dementia. In secondary care there are two instances where patients may be assessed for the presence of dementia - the general acute hospital setting, where opportunistic screening may be undertaken, or in specialist memory services where individuals have been referred due to perceived cognitive problems. This review determines the diagnostic accuracy of the informant‐based questionnaire IQCODE, for detection of all‐cause dementia in adults in secondary care services.

AD‐8 for detection of dementia across a variety of healthcare settings

Dementia assessment often involves initial screening, using a brief tool, followed by more detailed assessment where needed. The AD‐8 is a short questionnaire, completed by a suitable 'informant' who knows the person well, and is designed to assess change in functional performance secondary to cognitive change. This review aims to determine the accuracy of the AD‐8 questionnaire in detection of all‐cause dementia in adults.

Dementia test accuracy materials

Neuropsychological tests for the diagnosis of Alzheimer’s disease dementia and other dementias: a generic protocol for cross‐sectional and delayed‐verification studies

The design, conduct and reporting of a test accuracy systematic review is different to a standard review. If the test accuracy review has a dementia focus, there is added complexity.  This generic protocol offers a template for test accuracy reviews and includes guidance on some of the challenges specific to reviews in the dementia field.

Reporting standards for studies of diagnostic test accuracy in dementia: The STARDdem Initiative

Diagnostic criteria from Europe and the USA place greater emphasis on the use of biomarkers and imaging techniques in the diagnosis of Alzheimer’s disease in symptomatic and asymptomatic people. However, diagnostic tests for causes of cognitive problems are not restricted to biochemical and neuroimaging biomarkers, and there is a variety of clinical assessment scales for screening and diagnosis. As the dementia test accuracy literature grows, there is need to ensure consistency in reporting. A checklist of core aspects to be considered when describing dementia test research should aid interpretation, facilitate evidence synthesis and ultimately raise standards. This article aims to provide guidance on standards for reporting studies of diagnostic test accuracy for dementia disorders.

Development of an interactive web-based tool to conduct and interrogate meta-analysis of diagnostic test accuracy studies: MetaDTA

Recommended statistical methods for meta-analysis of diagnostic test accuracy (DTA) studies require relatively complex statistical models which can be a barrier for non-statisticians. Online tools offer accessibility and allow tailored interactivity. In this article the authors describe the development of a freely available web-based interactive tool, that has been recommended by Cochrane. The tool allows users to input DTA study data and conduct meta-analyses for DTA reviews, including sensitivity analyses. 

Blogposts on dementia screening tests

The Cochrane Dementia and Cognitive Improvement Group is passionate about sharing the results of our reviews beyond traditional academic circles. We work closely with the Evidently Cochrane team to create blogposts and other social media material. As test accuracy research can be difficult to explain, we have employed approaches ranging from patient stories to Lego! This section contains links to our specific blogposts on dementia screening tests:

About this Special Collection

References

1. Smailagic N, Vacante M, Hyde C, Martin S, Ukoumunne O, Sachpekidis C. ¹⁸F-FDG PET for the early diagnosis of Alzheimer's disease dementia and other dementias in people with mild cognitive impairment (MCI). Cochrane Database of Systematic Reviews 2015;(1):CD010632. https://doi.org/10.1002/14651858.CD010632.pub2

2. Ritchie C, Smailagic N, Noel-Storr AH, Ukoumunne O, Ladds EC, Martin S. CSF tau and the CSF tau/ABeta ratio for the diagnosis of Alzheimer's disease dementia and other dementias in people with mild cognitive impairment (MCI). Cochrane Database Systematic Reviews 2017; (3):CD010803. https://doi/10.1002/14651858.CD010803.pub2/full

3. McLeery J, Flicker L, Richard E, Quinn TJ. When is Alzheimer's not dementia-Cochrane commentary on The National Institute on Ageing and Alzheimer's Association Research Framework for Alzheimer's Disease. Age and Ageing 2019;48:174-77. https://doi.org/10.1093/ageing/afy167

4. Harrison JK, Noel-Storr AH, Demeyere N, Reynish El, Quinn TJ. Outcomes measures in a decade of dementia and mild cognitive impairment trials. Alzheimer’s Research & Therapy 2016;8:48. https://doi.org/10.1186/s13195-016-0216-8

Acknowledgements

This Special Collection was developed by Terence Quinn and the Cochrane Dementia and Cognitive Improvement group  (CDCIG) editorial team (Jenny McCleery, Sascha Köpke, Anna Noel-Storr, Candida Fenton and Sue Marcus) working with the Cochrane Editorial & Methods Department. The Cochrane Diagnostic Test Accuracy (DTA) Editorial Team provided specialist peer review for all the reviews in addition to CDCIG’s external clinical peer review. The reviews were supported by the National Institute for Health Research, via Cochrane Infrastructure funding and Cochrane Programme Grant funding to produce 15 DTA reviews for which Rupert McShane was the principle investigator. The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, NHS or Department of Health.

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Contact

Cochrane Editorial and Methods Department ([email protected])

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