Measurement Equivalence between the Original and Estimated Mini-Mental State Examination in People with Dementia

Background: The Cognitive Abilities Screening Instrument (CASI) is increasingly used to assess general cognitive function in people with dementia. The Mini-Mental State Examination (MMSE) score can be converted from the CASI (i.e., the estimated MMSE). Recognizing that measurement equivalence is critical to meaningfully representing one with the other, we aimed to determine whether the estimated MMSE score obtained from the CASI was equivalent to the original MMSE in people with dementia. Methods: We obtained 110 data points for the MMSE and CASI scores in people with dementia. The intraclass correlation coefficient (ICC), Pearson’s r, percent of standard error of measurement (SEM%), paired t-test, and effect size (Cohen’s d) were used to investigate the equivalence. Results: To examine the equivalence between the original and estimated MMSE score, the ICC and Pearson’s r of the total score and six domains were 0.62–0.95 and 0.62–0.96, respectively. The SEM% of the total score and six domains were 0.6–8.9%. The paired t-test results showed a significant difference (p < 0.05) between the total score and the three domains. The Cohen’s d of the total score and six domains were 0.06–0.27. Conclusions: The estimated MMSE score was found to have moderate to excellent equivalence to the original MMSE score. The three domains (i.e., registration, attention and calculation, and visual-constructional ability) with moderate equivalence should be used cautiously to interchange with the original MMSE in people with dementia.