Diagnostic accuracy of the "4 A's Test" delirium screening tool for the postoperative cardiac surgery ward

Background: Delirium is prevalent and underdetected among cardiac surgery patients on the postoperative ward. This study aimed to validate the 4 A's Test delirium screening tool and evaluate its accuracy both when used by research assistants and when subsequently implemented by nursing staff on the ward.

Methods: This single-center, prospective observational study evaluated the performance of the 4 A's Test administered by research assistants (phase 1) and nursing staff (phase 2). Assessments were undertaken during the patients' first 3 postoperative days on the postcardiac surgery ward along with previous routine nurse-led Confusion Assessment Method assessments. These index tests were compared with a reference standard diagnosis of delirium based on Diagnostic and Statistical Manual of Mental Disorders 5th Edition criteria. Surveys regarding delirium screening were administered to nurses pre- and postimplementation of the 4 A's Test in phase 2 of the study.

Results: In phase 1, a total of 137 patients were enrolled, of whom 24.8% experienced delirium on the postoperative cardiac ward. The 4 A's Test had a sensitivity of 85% (95% confidence interval, 73-93) and a specificity of 90% (95% confidence interval, 85-93) compared with the reference standard. The nurse-assessed Confusion Assessment Method had a sensitivity of 23% (95% confidence interval, 13-37) and specificity of 100% (95% confidence interval, 99-100). In phase 2, nurses (n = 51) screened 179 patients for delirium using the 4 A's Test. Compared with the reference rater, the 4 A's Test had a sensitivity of 58% (95% confidence interval, 28-85) and specificity of 94% (95% confidence interval, 85-98). Postimplementation, 64% of nurses thought that the 4 A's Test improved their confidence in delirium detection, and 76% of nurses would consider routine 4 A's Test use.

Conclusions: The 4 A's Test demonstrated moderate sensitivity and high specificity to detect delirium in a real-world setting after cardiac surgery on the postoperative ward. A modified model of use with less frequent administration, along with increased engagement of the postoperative team, is recommended to improve early delirium detection on the cardiac surgery postoperative ward.