The Delirium Interview as a new reference standard in studies on delirium assessment tools
Authors: Ditzel Fienke L. , Slooter Arjen J.C. , van den Boogaard Mark , Boonstra Michel , van Nesselrooij Timotheus A. , Kromkamp Marjan , Pop-Purceleanu Monica , Rood Paul J.T. , Osse Robert Jan. , Chan Carol K. , MacLullich Alasdair M.J. , Tieges Zoë , Neufeld Karin J. , Hut Suzanne C.A. 
Published: December 2022

Background

The reference standard in studies on delirium assessment tools is usually based on the clinical judgement of only one delirium expert, and may be concise, unstandardized, or not specified at all. This multicenter study investigated the performance of the Delirium Interview, a new reference standard for studies on delirium assessment tools, allowing classification of delirium based on written reports.

Methods

We tested the diagnostic accuracy of our standardized Delirium Interview by comparing delirium assessments of the reported results with live assessments. Our reference, the live assessment, was performed by two delirium experts and one well-trained researcher who registered the results. Their delirium assessment was compared with the majority vote of three other independent delirium experts who judged the rapportage of the Delirium Interview. Our total pool consisted of 13 delirium experts with an average of 13±8 years of experience.

Results

We included 98 patients (62% male, mean age 69±12 years), of whom 56 (57%) Intensive Care Units (ICU) patients, 22 (39%) patients with a Richmond Agitation Sedation Scale (RASS)<0 and 26 (27%) non-verbal assessments. The overall prevalence of delirium was 28%. The Delirium Interview had a sensitivity of 89% (95% Confidence Interval (CI): 71-98%) and specificity of 82% (95%CI: 71-90%), compared to the diagnosis of an independent panel of two delirium experts and one researcher who examined the patients themselves. Negative and positive predictive values were 95% (95%CI: 86-0.99%) respectively 66% (95%CI: 49-80%). Stratification into ICU and non-ICU patients yielded similar results.

Conclusion

The Delirium Interview is a feasible reference method for large study cohorts evaluating delirium assessment tools since experts could assess delirium with high accuracy without seeing the patient at the bedside.

Impact Statement

We certify that this work is novel because we propose a new reference standard for delirium assessment tools. It was developed based on an extensive dialogue with multiple delirium experts from different specialties (geriatrics, psychiatry, neurology, neuropsychology, critical care medicine, and nursing), composed from previously validated tests. It is novel in its approach of providing a logistically feasible method that serves as an accurate reference standard.

Key point box

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This paper proposes the Delirium Interview as a new reference for delirium assessment tools used at ICU and non-ICU departments.

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The diagnosis was based on the majority vote of an expert panel of three, accounting for the known disagreement on the diagnosis of delirium.

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Our panel could assess delirium with a high sensitivity of 89% (95% Confidence Interval (CI): 71-98%) and specificity of 82% (95%CI: 71-90%) without being present at the bedside.

Why does this paper matter?

Delirium is a major healthcare problem associated with longer hospital duration and increased healthcare costs. Recognition of delirium is essential for the treatment of underlying conditions and optimal communication with affected patients. The Delirium Interview is a reference method standardized for a heterogeneous population, including patients with low consciousness and intubated patients. The methodology is logistically efficient for studies with large cohorts, as we found that delirium experts could diagnose delirium with high accuracy without being present at bedside.