Undiagnosed delirium is frequent and difficult to predict: Results from a prevalence survey of a tertiary hospital

Peter W. Lange*, Marissa Lamanna, Rosie Watson, Andrea B. Maier

*Corresponding author for this work

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AIMS AND OBJECTIVES: To study the prevalence and determinants of undiagnosed delirium in a tertiary hospital.

BACKGROUND: Delirium is a common inpatient condition. It is frequently undiagnosed in a variety of settings, but determinants of undiagnosed delirium are largely unknown, and the frequency of undiagnosed delirium across all inpatient units is uncertain. The utility of hospital-wide screening then is also uncertain.

METHODS: Hospital-wide prevalence study conducted over 4 months, using a chart-based method. Gender, age, admitting unit, history of dementia and comorbidity were used in univariate and multivariate analyses to search for differences in patients with no delirium, with undiagnosed delirium and with diagnosed delirium. Sensitivity, specificity and number needed to screen were calculated from proportions in each group. Study was conducted in concordance with STROBE guidelines.

RESULTS: Delirium was prevalent in 12.5% of all patients and undiagnosed in 24.1% of patients. Only age ≥65 years and a history of dementia predicted delirium, and undiagnosed delirium in both univariate and multivariate analyses. Age ≥65 years accounts for 92.3% sensitivity and 50.8% specificity for undiagnosed delirium in this group. History of dementia had a 23.0% sensitivity and 97.0% specificity. Twenty-eight patients would need to be screened to detect a case of undiagnosed delirium.

DISCUSSION: There was a high rate of delirium and undiagnosed delirium in this cohort. Known risk factors for delirium also independently predict undiagnosed delirium; other factors were not found.

CONCLUSION: Undiagnosed delirium is common and difficult to predict from patient baseline characteristics other than age.

RELEVANCE TO CLINICAL PRACTICE: Assessment of all inpatients for delirium is recommended.

Original languageEnglish
Pages (from-to)2537-2542
Number of pages6
JournalJournal of Clinical Nursing
Issue number13-14
Early online date20 Feb 2019
Publication statusPublished - Jul 2019

Bibliographical note

© 2019 John Wiley & Sons Ltd.


The authors wish to thank the Royal Melbourne Hospital for financial support and assistance in the conduct of this study.

FundersFunder number
Royal Melbourne Hospital


    • Aged
    • Aged, 80 and over
    • Comorbidity
    • Cross-Sectional Studies
    • Delirium/diagnosis
    • Dementia/epidemiology
    • Female
    • Geriatric Assessment/methods
    • Humans
    • Male
    • Middle Aged
    • Prevalence
    • Risk Factors
    • Sensitivity and Specificity
    • Tertiary Care Centers/statistics & numerical data


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