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Tae Young Yeo, Keonyeup Kim, Moon Ho Park Department of Neurology, Korea University Ansan Hospital, Ansan, Republic of KoreaCorrespondence: Moon Ho ParkDepartment of Neurology, Korea University Ansan Hospital, 123 Jeokgeum-ro, Danwon-gu, Ansan-si, Gyeonggi-do 15355, Republic of KoreaTel +82 31 412 5155Fax +82 31 412 5154Email kmmse@naver.comPurpose: The ability to convert scores between cognitive measurements would facilitate the longitudinal assessment of cognition in clinical practice and the comparison and synthesis of cognitive data from international, multicenter, or longitudinal studies. The primary aim of this study was to apply a simple and reliable method for converting scores from the Korean Dementia Screening Questionnaire (KDSQ) to those of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE).Patients and methods: A total of 627 participants, with and without cognitive dysfunction, received both the KDSQ and the IQCODE at the same visit. The scores of both tools were calculated, and equipercentile equating was used to create a method for converting scores from the KDSQ to the IQCODE.Results: KDSQ scores were highly correlated with IQCODE scores (Pearson r = 0.905, P < 0.01). We developed scores for converting the KDSQ to the IQCODE using equipercentile equating and log-linear smoothing. We provide an easy-to-use table that enables the conversion of KDSQ scores to IQCODE scores.Conclusion: We delivered a simple and reliable method for converting scores from the KDSQ to the IQCODE. The conversion score table reported here enables direct and easy comparison of these cognitive measurements in older adults.Keywords: KDSQ, IQCODE, cognition, equation

Objective: The Korean Dementia Screening Questionnaire (KDSQ) is an informant-based instrument used to screen for cognitive dysfunction. However, its ability to only dichotomously discriminate between dementia and normal cognition has been previously investigated. This study investigated the ability of the KDSQ to classify not only dichotomous but also multiple stages of cognitive dysfunction., Methods: We examined 582 participants. Receiver operating characteristic (ROC) curves were used to determine dichotomous classification parameters. Multi-category ROC surfaces were evaluated to classify the three stages of cognitive dysfunction., Results: Dichotomous classification using the ROC curve analyses showed that the area under the curve was 0.92 for dementia for subjects without dementia and 0.96 for dementia in controls. Simultaneous multi-category classification analyses showed that the volume under the ROC surface (VUS) was 0.57 and that the derived optimal cut-off points were 2 and 8 for controls, MCI, and dementia. The estimated Youden index for the KDSQ was 0.48, and the derived optimal cut-off points were 5 and 10. The overall classification accuracy of the VUS and Youden index was 61.2% and 58.6%, respectively., Conclusion: The KDSQ is useful for classifying dichotomous and multi-category stages of cognitive dysfunction.