A brief cogntive screening test (Mini-Cog) for the assessment of possible dementia

With the aging of our populations there are increasing numbers of older adults with memory complaints and possible dementia. Identifying older adults who have dementia is important in order to help with planning their care needs and starting dementia specific treatments. In order to diagnose dementia, healthcare professionals or other service providers rely on tests of memory and other areas of cognition in combination with additional investigations. Brief memory tests, such as the Mini-Cog, may be useful as screening tests to help identify those individuals that might benefit from further evaluation in order to determine if dementia is present. The Mini-Cog is a brief cognitive test that involves an assessment of an older person's ability to recall three words and draw a clock. In this review, we searched medical literature databases to identify studies which evaluated how well the Mini-Cog is able to distinguish between individuals who have dementia and those who do not have dementia when compared to in-depth evaluation by dementia specialists. Our review focussed on those studies that were conducted in community based settings. We identified three unique randomised controlled studies that evaluated the Mini-Cog. In these studies the accuracy of the Mini-Cog varied and importantly there were some potential limitations within the studies which may have led to an overestimation of the accuracy of the Mini-Cog. Based on the information that we obtained from our review, we felt that further research into the accuracy of the Mini-Cog was required before it could be recommended for routine use for identifying dementia in community settings.

Authors' conclusions: 

There are currently few studies assessing the diagnostic test accuracy of the Mini-Cog in community settings. The limited number of studies and the methodological limitations that are present in the current studies make it difficult to provide recommendations for or against the use of the Mini-Cog as a cognitive screening test in community settings. Additional well-designed studies comparing the Mini-Cog to other brief cognitive screening tests are required in order to determine the accuracy and utility of the Mini-Cog in community based settings.

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Background: 

Alzheimer's disease and related forms of dementia are becoming increasingly prevalent with the aging of many populations. The diagnosis of Alzheimer's disease relies on tests to evaluate cognition and discriminate between individuals with dementia and those without dementia. The Mini-Cog is a brief, cognitive screening test that is frequently used to evaluate cognition in older adults in various settings.

Objectives: 

The primary objective of this review was to determine the diagnostic accuracy of the Mini-Cog for detecting Alzheimer's disease dementia and related dementias in a community setting.

Secondary objectives included investigations of the heterogeneity of test accuracy in the included studies and potential sources of heterogeneity. These potential sources of heterogeneity included the baseline prevalence of dementia in study samples, thresholds used to determine positive test results, the type of dementia (Alzheimer's disease dementia or all causes of dementia), and aspects of study design related to study quality. Overall, the goals of this review were to determine if the Mini-Cog is a cognitive screening test that could be recommended to screen for cognitive impairment in community settings.

Search strategy: 

We searched MEDLINE (OvidSP), EMBASE (OvidSP), PsycINFO (Ovid SP), Science Citation Index (Web of Science), BIOSIS previews (Web of Science), LILACS (BIREME), and the Cochrane Dementia Group's developing register of diagnostic test accuracy studies to March 2013. We used citation tracking (using the database’s ‘related articles’ feature, where available) as an additional search method and contacted authors of eligible studies for unpublished data.

Selection criteria: 

We included all cross-sectional studies that utilized the Mini-Cog as an index test for the diagnosis of dementia when compared to a reference standard diagnosis of dementia using standardized dementia diagnostic criteria. For the current review we only included studies that were conducted on samples from community settings, and excluded studies that were conducted in primary care or secondary care settings. We considered studies to be conducted in a community setting where participants were sampled from the general population.

Data collection and analysis: 

Information from studies meeting the inclusion criteria were extracted including information on the characteristics of participants in the studies. The quality of the studies was assessed using the QUADAS-2 criteria and summarized using risk of bias applicability and summary graphs. We extracted information on the diagnostic test accuracy of studies including the sensitivity, specificity, and 95% confidence intervals of these measures and summarized the findings using forest plots. Study specific sensitivities and specificities were also plotted in receiver operating curve space.

Main results: 

Three studies met the inclusion criteria, with a total of 1620 participants. The sensitivities of the Mini-Cog in the individual studies were reported as 0.99, 0.76 and 0.99. The specificity of the Mini-Cog varied in the individual studies and was 0.93, 0.89 and 0.83. There was clinical and methodological heterogeneity between the studies which precluded a pooled meta-analysis of the results. Methodological limitations were present in all the studies introducing potential sources of bias, specifically with respect to the methods for participant selection.

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