The Delirium Interview as a new reference standard in studies on delirium assessment tools

Background: The reference standard in studies on delirium assessment tools is usually based on the clinical judgment 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 to 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 (ICUs) 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.