The current findings suggest that the traditional MMSE cut-score of 24 does not yield optimal classification accuracy in highly educated Caucasian dementia patients. Instead, a more stringent cut-score of 27 yields greater clinical utility with regard to identifying dementia in well-educated individuals. Although there is an expected concomitant increase in false-positive identifications using the higher cut score, a sacrifice in specificity in exchange for a significant gain in sensitivity is preferred when the goal of the mental status screen is early detection of possible dementia.
The current analyses also demonstrate that, when MCI is entered into the equation, obtaining an optimal balance between SN and SP is very difficult indeed. demonstrates that optimal balances between SN and SP are found at cut-scores of either 27 (SN=.69, SP=.91) or 28 (SN and SP = .78). One might note that the NPV and PPV for the cognitively impaired group using the traditional cut-score of 24 is quite impressive even at low base rates; however, this is a function of a perfect SP and the low base rates. What this translates to for practicing clinicians is a very high false negative rate (often 50% or more) meaning that, because of the small number of true cases in low base rate settings, a large portion of those individuals actually suffering from cognitive dysfunction will not be detected and referred on for a comprehensive evaluation and/or treatment. allows the individual clinician to make the determination as to what cut-score(s) s/he wishes to implement given the nature of the clinic population (e.g., demographics, appropriate base rate), additional information obtained in the medical examination (i.e., screening for cognitive impairment versus dementia if information regarding functional change is obtained), as well as his/her preferences for potential diagnostic error (i.e., false negative and false positive rates).
The vast majority of the published literature examining the relationship between cognitive test performance and education focuses on lower educated populations without consideration to individuals who have obtained high levels of education. In fact, research suggests that lower cut-scores on the MMSE are appropriate when evaluating populations obtaining lower levels of education11
and correction formulas have been published5
. Educational attainment is often considered one manifestation of cognitive reserve, with higher education levels associated with greater reserve and greater ability to withstand neuropathological burden before exhibiting detectable signs of disease (see Stern13
for review). Individuals with greater cognitive reserve are believed to maintain higher levels of cognitive functioning in the early stages of degenerative dementia. By the time cognitive symptoms are first identified, these patients are believed to have significantly greater disease burden and faster subsequent decline. Identifying such individuals at an earlier stage of disease development and progression is desirable for both treatment and research purposes.
There was not enough data in the current sample to test the comparative accuracy of individual cut-scores among highly educated individuals across ethnic groups. Therefore, the current findings with Caucasian individuals must be tested within ethnic minority populations before generalizations can be made. Additionally, the sample is an English-speaking sample and caution must be used when attempting to generalize to English as a second language or non-English speaking individuals. It should also be noted that the MMSE was administered as part of the clinical examination and was not used as part of the inclusion/exclusion criteria for the study database. Therefore, the MMSE was not used as a screening measure of cognitive functioning in this sample and might perform differently when used in this context (e.g., epidemiological studies).
The current findings are not intended to encourage the diagnosis of cognitive impairment or dementia based on total MMSE scores alone. Instead these results provide practitioners with revised criteria for appropriate management of highly educated Caucasian elders. Specifically, older patients who present with memory complaints (self- or other-report) that have attained a college degree or higher level of education and who score below 27 on the MMSE are at increased risk of cognitive dysfunction and dementia and should be referred for a comprehensive evaluation, including formal neuropsychological studies. When early identification is the primary goal of screening, the cost associated with performing further evaluation on individuals subsequently found to have no dementia is outweighed by the benefit of identifying a considerably larger number of individuals who are in the earliest stages of dementia, where early intervention and/or participation in clinical trials may provide maximum benefit.