# Calibrating Mini-Mental State Examination Scores to Predict Misdiagnosed Dementia Patients
## 2 Literature Review  
### Mini-Mental State Examination  
The MMSE was first introduced in 1975 [4] as a clinical approach to quantifying the cognitive status of patients with suspected neuro-degenerative dementias. Its diagnostic properties have been replicated in a number of studies, both in its original English format and after adaptations for use in other languages. It has since been adopted as a routine component of the cognitive assessment of patients with Mild Cognitive Impairment (MCI) or AD, in the context of both clinical evaluation and research studies. A rival method of screening for and evaluating patients with dementia is the Clock Drawing Test (CDT) [14]. The CDT provides a simple scoring system for the rapid screening of cognitive impairment in patients with MCI and Dementia [15]. The MMSE has also become the most popular and widely used screening instrument in dementia [10], with the cutoff of 26 being defined as distinguishing cognitively normal people from those with incipient or established dementia. A value of 27 is used in subpopulations with high levels of education [16]. The MMSE can also be used to delineate the different stages of AD, with a score of 20 to 24 suggesting mild dementia, 13 to 20 suggesting moderate dementia, and less than 12 indicating severe [17]. The MMSE has good sensitivity and specificity across all age and educational groups [18]. In contrast, the Montreal Cognitive Assessment (MoCA), an alternative brief cognitive screening tool, which is also scored out of 30, may be more sensitive at discriminating MCI and Alzheimer's Disease, but has lower specificity, misclassifying more cognitively normal elderly controls than the MMSE [5]. MMSE has been also validated in dementia other than AD--e.g., dementia with Lewy Bodies and Parkinson's disease dementia [19]--and has neurophysiological correlates: a recent study [20] found that a combination of the peak latency of the p300 component of an event-related potential, and the power associated with the alpha frequency of the electroencephalogram, together with age and years of education, were able to predict the MMSE score with an accuracy of three points. [PERSON] et al. [8] studied the role of MMSE as a predictor of which patients diagnosed with the prodormal syndrome of MCI would go on to develop dementia. Although a one-off test score is unlikely to have much predictive power to answer this question, monitoring the rate of change over time may be more informative, suggesting that the role of repeated MMSE measurements could prove more informative than single baseline scores. A review by [PERSON] et al. [21] also attempted to determine the diagnostic accuracy of MMSE at various cut points for dementia in people aged 65 years and over. The authors concluded that MMSE contributes to a diagnosis of dementia in low prevalence settings, but should not be used in isolation to confirm or exclude disease. It was also proposed that it would be important for future investigators to understand whether administering the MMSE changes patient-relevant outcomes. Most of the above work will have been conducted prospectively, using dedicated test protocols carried out by trained individuals, and therefore not likely to contain inaccuracies. However, the power and versatility of the MMSE is such that values recorded in electronic patient records, and therefore available as a component of big data resources, could be exploited to interrogate a variety of clinical and biological questions from a fresh perspective. Such values are, however, typically obtained during clinical visits, often under time pressure, and by individuals with different approaches to testing and scoring, and therefore may be subject to variability and/or inaccuracy. In this paper, we report work investigating serial MMSE tests in a cohort of patients at various stages of dementia, in order to identify instances of misdiagnosis in the form of MMSE score miscalculations.