Delirium detection in older acute medical inpatients: a multicentre prospective comparative diagnostic test accuracy study of the 4AT and the confusion assessment method

Abstract

Background: Delirium affects > 15% of hospitalised patients but is grossly underdetected, contributing to poor care. The 4 'A's Test (4AT, www.the4AT.com ) is a short delirium assessment tool designed for routine use without special training. The primary objective was to assess the accuracy of the 4AT for delirium detection. The secondary objective was to compare the 4AT with another commonly used delirium assessment tool, the Confusion Assessment Method (CAM).

Methods: This was a prospective diagnostic test accuracy study set in emergency departments or acute medical wards involving acute medical patients aged ≥ 70. All those without acutely life-threatening illness or coma were eligible. Patients underwent (1) reference standard delirium assessment based on DSM-IV criteria and (2) were randomised to either the index test (4AT, scores 0-12; prespecified score of > 3 considered positive) or the comparator (CAM; scored positive or negative), in a random order, using computer-generated pseudo-random numbers, stratified by study site, with block allocation. Reference standard and 4AT or CAM assessments were performed by pairs of independent raters blinded to the results of the other assessment.

Results: Eight hundred forty-three individuals were randomised: 21 withdrew, 3 lost contact, 32 indeterminate diagnosis, 2 missing outcome, and 785 were included in the analysis. Mean age was 81.4 (SD 6.4) years. 12.1% (95/785) had delirium by reference standard assessment, 14.3% (56/392) by 4AT, and 4.7% (18/384) by CAM. The 4AT had an area under the receiver operating characteristic curve of 0.90 (95% CI 0.84-0.96). The 4AT had a sensitivity of 76% (95% CI 61-87%) and a specificity of 94% (95% CI 92-97%). The CAM had a sensitivity of 40% (95% CI 26-57%) and a specificity of 100% (95% CI 98-100%).

Conclusions: The 4AT is a short, pragmatic tool which can help improving detection rates of delirium in routine clinical care.

Trial registration: International standard randomised controlled trial number (ISRCTN) 53388093 . Date applied 30/05/2014; date assigned 02/06/2014.

Keywords: 4AT; Confusion assessment method (CAM); Delirium; Diagnostic test accuracy; Hospital; Sensitivity; Specificity.

Fig. 1

The 4 ‘A’s Test (4AT)

Fig. 2

Diagnostic accuracy study: overview flowchart. ED, Emergency Department; MOE, Medicine of the Elderly; 4AT, 4 ‘A’s Test; CAM, Confusion Assessment Method

Fig. 3

STARD diagram of the flow of participants through the study (total across all three sites)

Fig. 4

Receiver operator characteristic curve for 4AT diagnostic accuracy. 4AT scores range from 0 to 12. The cut-point of > 3 is used in the scoring scheme to denote likely delirium. The 4AT scores are considered against the reference standard delirium assessment