Four sensitive screening tools to detect cognitive dysfunction in geriatric emergency department patients: brief Alzheimer's Screen, Short Blessed Test, Ottawa 3DY, and the caregiver-completed AD8

Abstract

Background: Cognitive dysfunction, including dementia and delirium, is prevalent in geriatric emergency department (ED) patients, but often remains undetected. One barrier to reliable identification of acutely or chronically impaired cognitive function is the lack of an acceptable screening tool. While multiple brief screening instruments have been derived, ED validation trials have not previously demonstrated tools that are appropriately sensitive for clinical use.

Objectives: The primary objective was to evaluate and compare the Ottawa 3DY (O3DY), Brief Alzheimer's Screen (BAS), Short Blessed Test (SBT), and caregiver-completed AD8 (cAD8) diagnostic test performance for cognitive dysfunction in geriatric ED patients using the Mini Mental Status Exam (MMSE) as the criterion standard. A secondary objective was to assess the diagnostic accuracy for the cAD8 (which is an informant-based instrument) when used in combination with the other performance-based screening tools.

Methods: In an observational cross-sectional cohort study at one urban academic university-affiliated medical center, trained research assistants (RAs) collected patients' responses on the Confusion Assessment Method for the Intensive Care Unit, BAS, and SBT. When available, reliable caregivers completed the cAD8. The MMSE was then obtained. The O3DY was reconstructed from elements of the MMSE and the BAS. Consenting subjects were non-critically ill, English-speaking adults over age 65 years, who had not received potentially sedating medications prior to or during cognitive testing. Using an MMSE score of ≤23 as the criterion standard for cognitive dysfunction, the sensitivity, specificity, likelihood ratios, and receiver operating characteristic (ROC) area under the curve (AUC) were computed. Venn diagrams were constructed to quantitatively compare the degree of overlap among positive test results between the performance-based instruments.

Results: The prevalence of cognitive dysfunction for the 163 patients enrolled with complete data collection was 37%, including 5.5% with delirium. Dementia was self-reported in 3%. Caregivers were available to complete the cAD8 for 56% of patients. The SBT, BAS, and O3DY each demonstrated 95% sensitivity, compared with 83% sensitivity for the cAD8. The SBT had a superior specificity of 65%. No combination of instruments with the cAD8 significantly improved diagnostic accuracy. The SBT provided the optimal overlap with the MMSE.

Conclusions: The SBT, BAS, and O3DY are three brief performance-based screening instruments to identify geriatric patients with cognitive dysfunction more rapidly than the MMSE. Among these three instruments, the SBT provides the best diagnostic test characteristics and overlap with MMSE results. The addition of the cAD8 to the other instruments does not enhance diagnostic accuracy.

© 2011 by the Society for Academic Emergency Medicine.

Figures

Figure 1

Flow Diagram for Patient Enrollment

Figure 2. Venn Diagram for Abnormal Cognitive Screening Tests

All subjects in this Venn diagram had abnormal cognitive screening test results. The overlapping regions of the rectangles represent agreement between the various instruments and are proportional to the actual results. The following key depicts the regions of agreement. The caregiver-taken Alzheimer’s Disease-8 (cAD8) was excluded from this analysis because not every subject had a cAD8 completed. A = Mini Mental Status Exam (MMSE) only abnormal B = Short Blessed Test (SBT) only abnormal C = Brief Alzheimer’s Screen (BAS) only abnormal D = Ottawa 3-Day-Year (O3DY) only abnormal E = MMSE and SBT abnormal F = MMSE and BAS abnormal G = SBT and BAS abnormal H = MMSE and O3DY abnormal I = SBT and O3DY abnormal J = O3DY and BAS abnormal K = MMSE, SBT, and BAS abnormal L = MMSE, O3DY, and SBT abnormal M = MMSE, BAS, and O3DY abnormal N = SBT, O3DY, and BAS abnormal O = MMSE, SBT, BAS, and O3DY abnormal

Figure 3

ROC Curves for SBT, BAS, and cAD8* AUC (95% CI)BAS0.934 (0.867–0.974)SBT0.930 (0.862–0.971)cAD80.816 (0.727–0.886)† *N= 102 subjects who completed the MMSE, SBT, and BAS and had a caregiver present to complete the cAD8. †cAD8 ROC AUC differs significantly from BAS (p = 0.01) and SBT (p = 0.008). ROC = receiver operating characteristic; SBT = Short Blessed Test; BAS = Basic Alzheimer’s Screen; cAD8 = caregiver-completed Alzheimer’s Disease -8; AUC = area under the ROC curve