Department of Emergency Medicine; Graduate School of Biomedical Sciences
Diagnosis | Emergency Medicine | Geriatrics | Health Services Administration | Mental Disorders | Pathological Conditions, Signs and Symptoms | Psychiatry and Psychology
BACKGROUND: This study aimed to describe the level of agreement of three commonly used delirium instruments: the Delirium Rating Scale-Revised-98 (DRS-R-98), Memorial Delirium Assessment Scale (MDAS), and Confusion Assessment Method-Severity (CAM-S).
METHODS: We used data from a prospective clinical research study, in which a team of trained lay interviewers administered each instrument along with supporting interview and cognitive assessments in the same group of patients daily while in the hospital (N = 352). We used item response theory methods to co-calibrate the instruments.
RESULTS: The latent traits underlying the three measures, capturing the severity of a delirium assessment, had a high degree of correlation (r's > .82). Unidimensional factor models fit well, facilitating co-calibration of the instruments. Across instruments, the less intense symptoms were generally items reflecting cognitive impairment. Although the intensity of delirium severity for most in the sample was relatively low, many of the item thresholds for the delirium severity scales are high (i.e., in the more severe range of the latent ability distribution). This indicates that even people with severe delirium may have a low probability of endorsing the highest severity categories for many items. Co-calibration enabled us to derive crosswalks to map delirium severity scores among the delirium instruments.
CONCLUSION: These delirium instruments measure the same underlying construct of delirium severity. Relative locations of items may inform design of refined measurement instruments. Mapping of overall delirium severity scores across the delirium severity instruments enabled us to derive crosswalks, which allow scores to be translated across instruments, facilitating comparison and combination of delirium studies for integrative analysis.
Delirium, Elderly, Item response theory, Psychometrics, Severity
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© The Author(s). 2018 Open Access: This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
DOI of Published Version
BMC Med Res Methodol. 2018 Sep 10;18(1):92. doi: 10.1186/s12874-018-0552-4. Link to article on publisher's site
BMC medical research methodology
Gross AL, Tommet D, D'Aquila M, Schmitt E, Marcantonio ER, Helfand B, Inouye SK, Jones RN. (2018). Harmonization of delirium severity instruments: a comparison of the DRS-R-98, MDAS, and CAM-S using item response theory. Open Access Articles. https://doi.org/10.1186/s12874-018-0552-4. Retrieved from https://escholarship.umassmed.edu/oapubs/3610
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.