Conversion between Mini‐Mental State Examination and Montreal Cognitive Assessment scores in older adults undergoing selective surgery using Rasch analysis

Abstract

Aims: To develop and validate a conversion table between the MMSE and the MoCA using Rasch analysis in older adults undergoing selective surgery and examine its diagnostic accuracy in detecting cognitive impairment. Design: Cross-sectional study. Methods: Older patients [N = 129; age 66.0 (4.6) years, education 7.7 (3.5) years] undergoing elective surgery were recruited from December 2017 to June 2018. All participants completed the MMSE and MoCA and 113 of them completed a battery of neuropsychological tests. Common person linking based on Rasch analysis was performed to develop the conversion table. The conversions were validated by calculating the intraclass correlation coefficient (ICC), score differences between actual and converted scores, and root mean squared error of the difference (RMSE). The diagnostic accuracy of the conversions for detecting cognitive impairment was also tested. Results: The MoCA [person measure: 1.3 (1.1) logits] was better targeted to the patients than the MMSE [person measure: 3.2 (1.3) logits]. Conversion from MoCA to MMSE scores (ICC 0.84, 95% CI 0.77-0.88; RMSE 1.36) was more precise than conversion from MMSE to MoCA (ICC 0.82, 95% CI 0.75-0.87; RMSE 2.56). Conversion from MoCA to MMSE demonstrated better diagnostic accuracy in detecting cognitive impairment than the actual MMSE, whereas conversion from MMSE to MoCA exhibited the opposite pattern. Conclusion: Conversion from MoCA to MMSE was more precise and had better diagnostic accuracy in detecting pre-operative cognitive impairment in older patients undergoing selective surgery than conversion from MMSE into MoCA. Impact: The finding is useful for interpreting, comparing, and integrating cognitive measurements in surgical settings and clinical research. Statistically sound conversion between MoCA and MMSE based on Rasch analysis is now possible for surgical setting and clinical research.

Conversion between the Montreal Cognitive Assessment and the Mini‐Mental Status Examination

“…This is consistent with other existing conversion tables 3,12,17–18 . Previous studies documented lower reliability for the MMSE‐MoCA conversion than for the reverse equation 17,36 . In the present analysis, prediction of MoCA scores from MMSE data was also less accurate.…”

“…3,12,[17][18] Previous studies documented lower reliability for the MMSE-MoCA conversion than for the reverse equation. 17,36 In the present analysis, prediction of MoCA scores from MMSE data was also less accurate. Overall, the MMSE-MoCA conversion table presented here replicates existing tables for clinically heterogeneous samples with different neurodegenerative 17,24 and neurological diseases.…”

“…Equivalent MMSE scores >30 points 9,27 and equivalent MoCA scores <0 27 must be set to 0/0 points and 30/30 points to facilitate clinical interpretation. Another point to mention is, that the majority of existing studies provide conversion tables for specific patient populations 12–14,16,18–19,27,36 . This is based on the assumption that the association between MoCA and MMSE is expected to differ between patients with primarily mnestic disorders and patients with executive dysfunction, since executive functions are not assessed in the MMSE 13,17,24 .…”

“…Another point to mention is, that the majority of existing studies provide conversion tables for specific patient populations. [12][13][14]16,[18][19]27,36 This is based on the assumption that the association between MoCA and MMSE is expected to differ between patients with primarily mnestic disorders and patients with executive dysfunction, since executive functions are not assessed in the MMSE. 13,17,24 It is possible that etiology-specific conversion tables are more reliable when the cause of the cognitive disorder is known.…”

“…17 Nevertheless, our results are comparable to a previous study, where the test administration did not take place in a fixed order to prevent exhaustion effects. 36 Fourth, the MMSE and MoCA in this study were both administered in a specific language and in specific versions, which can lead to a limited generalizability. However, the generalizability of the score conversion compared with other languages seems to have some consistency.…”