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The Confusion Assessment Method for the ICU-7 Delirium Severity Scale: A Novel Delirium Severity Instrument for Use in the ICU

Khan, Babar A. MD, MS1–3; Perkins, Anthony J. MS4; Gao, Sujuan PhD1; Hui, Siu L. PhD3; Campbell, Noll L. PharmD2,3,5,6; Farber, Mark O. MD1; Chlan, Linda L. PhD7; Boustani, Malaz A. MD, MPH1–4

doi: 10.1097/CCM.0000000000002368
Clinical Investigations

Objectives: Delirium severity is independently associated with longer hospital stays, nursing home placement, and death in patients outside the ICU. Delirium severity in the ICU is not routinely measured because the available instruments are difficult to complete in critically ill patients. We designed our study to assess the reliability and validity of a new ICU delirium severity tool, the Confusion Assessment Method for the ICU-7 delirium severity scale.

Design: Observational cohort study.

Setting: Medical, surgical, and progressive ICUs of three academic hospitals.

Patients: Five hundred eighteen adult (≥ 18 yr) patients.

Interventions: None.

Measurements and Main Results: Patients received the Confusion Assessment Method for the ICU, Richmond Agitation-Sedation Scale, and Delirium Rating Scale-Revised-98 assessments. A 7-point scale (0–7) was derived from responses to the Confusion Assessment Method for the ICU and Richmond Agitation-Sedation Scale items. Confusion Assessment Method for the ICU-7 showed high internal consistency (Cronbach’s α = 0.85) and good correlation with Delirium Rating Scale-Revised-98 scores (correlation coefficient = 0.64). Known-groups validity was supported by the separation of mechanically ventilated and nonventilated assessments. Median Confusion Assessment Method for the ICU-7 scores demonstrated good predictive validity with higher odds (odds ratio = 1.47; 95% CI = 1.30–1.66) of in-hospital mortality and lower odds (odds ratio = 0.8; 95% CI = 0.72–0.9) of being discharged home after adjusting for age, race, gender, severity of illness, and chronic comorbidities. Higher Confusion Assessment Method for the ICU-7 scores were also associated with increased length of ICU stay (p = 0.001).

Conclusions: Our results suggest that Confusion Assessment Method for the ICU-7 is a valid and reliable delirium severity measure among ICU patients. Further research comparing it to other delirium severity measures, its use in delirium efficacy trials, and real-life implementation is needed to determine its role in research and clinical practice.

Supplemental Digital Content is available in the text.

1Indiana University School of Medicine, Indianapolis, IN.

2Indiana University Center for Aging Research, Indianapolis, IN.

3Regenstrief Institute, Inc., Indianapolis, IN.

4Indiana University Center for Health Innovation and Implementation Science, Indiana Clinical and Translational Sciences Institute, Indianapolis, IN.

5Eskenazi Health, Indianapolis, IN.

6Department of Pharmacy Practice, Purdue University College of Pharmacy, West Lafayette, IN.

7Nursing Research Division, Department of Nursing, Mayo Clinic, Rochester, MN.

This work was performed at Indiana University School of Medicine, Indianapolis, IN.

Supported, in part, by a grant from the National Institute on Aging (R01AG034205), awarded to Dr. Boustani. Dr. Khan’s work on the project was supported through a Career Development Award from the National Institute on Aging (NIA K23-AG043476).

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s website (

Drs. Khan, Perkins, Gao, Hui, and Campbell received support for article research from the National Institutes of Health (NIH). Dr. Khan’s institution received funding from National Institute on Aging (R01AG034205) and from National Institute on Aging (NIA) Career Development Award (NIA K23-AG043476). Dr. Perkins’ institution received funding from NIH, NIH/NIA, and CMS. Dr. Gao’s institution received funding from NIH. Dr. Hui’s institution received funding from NIH. Dr. Campbell’s institution received funding from Astellas Pharma US. Dr. Chlan received funding from Yale University (for visiting professor honorarium March 2015) and from Critical Care Alert (Associate Editor, paid for each contribution). The remaining authors have disclosed that they do not have any potential conflicts of interest.

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