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

Abstract

Background and PurposeThere 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.MethodsWe 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.ResultsThe 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.ConclusionsWe 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.