Validation of Four Methods for Converting Scores on the Montreal Cognitive Assessment to Scores on the Mini-Mental State Examination-2.

Background and purpose: There are many methods for converting scores from the Montreal Cognitive Assessment (MoCA) to those on the Mini-Mental State Examination (MMSE). In this study we aimed to validate 4 methods that convert the full score range (0-30 points) of the MoCA to an equivalent range for the MMSE.

Methods: We examined the medical records of 506 subjects who completed the MoCA and MMSE-second edition (MMSE-2) on the same day. For the validation index, we calculated mean, median, and root-mean-squared error (RMSE) of the difference between true and equivalent MMSE-2 scores. We also calculated intraclass correlation coefficients (ICCs), the Bland-Altman plot, and the generalizability coefficient between true and equivalent MMSE-2 scores for reliability. We compared the ICCs according to age, sex, education, MMSE, and cognitive-status subgroups. For accuracy, we evaluated a ±2 point difference between the true and equivalent MMSE-2 scores.

Results: The 4 conversion methods had a mean of -0.79 to -0.05, a median of -1 to 0, and an RMSE of 2.61-2.94 between true and equivalent MMSE-2 scores. All conversion methods had excellent reliability, with an ICC greater than 0.75 between true and equivalent MMSE-2 scores. These results were almost maintained in the subgroup analyses. These conversion methods provided more than 65% accuracy within ±2 points of the true MMSE-2 scores.

Conclusions: We suggest that these 4 conversion methods are applicable for converting MoCA scores to MMSE-2 scores. They will greatly enhance the usefulness of existing cognitive data in clinical and research settings.