Diagnosing Delirium in Older Emergency Department Patients: Validity and Reliability of the Delirium Triage Screen and the Brief Confusion Assessment Method

Study objective

Delirium is a common form of acute brain dysfunction with prognostic significance. Health care professionals caring for older emergency department (ED) patients miss delirium in approximately 75% of cases. This error results from a lack of available measures that can be performed rapidly enough to be incorporated into clinical practice. Therefore, we developed and evaluated a novel 2-step approach to delirium surveillance for the ED.

Methods

This prospective observational study was conducted at an academic ED in patients aged 65 years or older. A research assistant and physician performed the Delirium Triage Screen (DTS), designed to be a highly sensitive rule-out test, and the Brief Confusion Assessment Method (bCAM), designed to be a highly specific rule-in test for delirium. The reference standard for delirium was a comprehensive psychiatrist assessment using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision criteria. All assessments were independently conducted within 3 hours of one another. Sensitivities, specificities, and likelihood ratios with their 95% confidence intervals (95% CIs) were calculated.

Results

Of 406 enrolled patients, 50 (12.3%) had delirium diagnosed by the psychiatrist reference standard. The DTS was 98.0% sensitive (95% CI 89.5% to 99.5%), with an expected specificity of approximately 55% for both raters. The DTS's negative likelihood ratio was 0.04 (95% CI 0.01 to 0.25) for both raters. As the complement, the bCAM had a specificity of 95.8% (95% CI 93.2% to 97.4%) and 96.9% (95% CI 94.6% to 98.3%) and a sensitivity of 84.0% (95% CI 71.5% to 91.7%) and 78.0% (95% CI 64.8% to 87.2%) when performed by the physician and research assistant, respectively. The positive likelihood ratios for the bCAM were 19.9 (95% CI 12.0 to 33.2) and 25.2 (95% CI 13.9 to 46.0), respectively. If the research assistant DTS was followed by the physician bCAM, the sensitivity of this combination was 84.0% (95% CI 71.5% to 91.7%) and specificity was 95.8% (95% CI 93.2% to 97.4%). If the research assistant performed both the DTS and bCAM, this combination was 78.0% sensitive (95% CI 64.8% to 87.2%) and 97.2% specific (95% CI 94.9% to 98.5%). If the physician performed both the DTS and bCAM, this combination was 82.0% sensitive (95% CI 69.2% to 90.2%) and 95.8% specific (95% CI 93.2% to 97.4%).

Conclusion

In older ED patients, this 2-step approach (highly sensitive DTS followed by highly specific bCAM) may enable health care professionals, regardless of clinical background, to efficiently screen for delirium. Larger, multicenter trials are needed to confirm these findings and to determine the effect of these assessments on delirium recognition in the ED.

Introduction

Delirium is an acute disturbance in attention accompanied by a rapid change in cognition that affects 1.5 million older emergency department (ED) patients in the United States annually.1, 2, 3 This form of acute brain dysfunction often leads to devastating consequences such as death and accelerated cognitive decline.4, 5, 6 Unfortunately, delirium is frequently missed by health care professionals in all clinical settings,2, 7 which is especially the case in the ED, where it is missed 57% to 83% of the time.2, 8, 9, 10, 11, 12, 13

The ED is the nexus of the health care system.¹⁴ Missing delirium in this setting has the potential to compromise patient safety and may have downstream implications for clinical care and patient health.¹⁵ Because delirious patients are less likely to provide an accurate reason of why they are in the ED, missing delirium may lead to inadequate diagnostic evaluations, inappropriate dispositions, and delays in the diagnosis of their underlying medical illness.16, 17 Up to 25% of delirious ED patients are discharged home2, 12, 18 and are less likely to comprehend their discharge instructions, which may lead to decreased compliance.16, 19 Finally, if patients are admitted, delirium that is missed in the ED will also be missed in the inpatient setting in more than 90% of cases.¹³

Delirium is often clinically silent and will remain unrecognized without a formal delirium assessment. Most health care professionals do not screen for delirium in their clinical practice13, 20 because there is a dearth of brief and easy-to-use assessments. Many existing assessments take more than 5 minutes to complete and may not be feasible to perform in busy clinical environments.²¹ Because physicians often evaluate a large number of patients in a short period of time, nonphysician hospital personnel (nurses, patient care technicians, etc) who have more exposure to patients may be better suited for delirium screening. Unfortunately, most delirium assessments are subjective and their diagnostic accuracy may be reduced when used by nonphysicians.22, 23

One method to improve delirium detection would be to use a 2-step approach: a sequential testing strategy that uses brief, valid, and reliable delirium assessments that can be performed by health care professionals of all clinical backgrounds. The first step would be to perform a very brief (<20 seconds), highly sensitive delirium screen to rule out delirium. This rapid rule-out screen can be incorporated into the ED triage assessment or can be part of the initial nursing assessment after the patient has been assigned an ED bed. A negative screen result would rule out delirium, reduce the number of formal delirium assessments needed, and enhance screening efficiency. A positive screen result would trigger a formal delirium assessment performed by another health care provider (ie, physician) at the patient's bedside that would be highly specific to rule in delirium. Ideally, this rule-in assessment should be brief (<1 minute) to maximize feasibility. We developed Delirium Triage Screen (DTS) and the Brief Confusion Assessment Method (bCAM) to serve as the rule-out and rule-in tests for the 2-step approach to delirium surveillance (Figure 1), respectively.

We sought to determine the diagnostic performances of these novel assessments in older ED patients, using the psychiatrist's assessment as the reference standard.