NEWS2 shows low sensitivity and high specificity for delirium detection: a single site observational study of 13,908 patients.

Delirium affects 25% of hospital admissions of older people and is a serious medical condition with poor outcomes. 'New confusion' as a delirium indicator was incorporated into the 'alert, verbal, pain and unresponsive' (AVPU) level of consciousness scale in the National Early Warning Score 2 (NEWS2) in 2017. We measured sensitivity of non-alert NEWS2 (new confusion and/or V, P or U ratings) for delirium through comparison with the four 'A's test (4AT) delirium tool in 13,908 consecutive non-elective hospital admissions. We included NEWS2 scores 4 hours before or after 4AT. There were 2,802 (20%) admissions with positive 4AT and 594 (4.3%) with non-alert NEWS2 status. Sensitivity of NEWS2 for 4AT ≥4 was 17.8% (95% confidence interval (CI) 16.4-19.2), and specificity was 99.1% (95% CI 98.9-99.3). These findings suggest that NEWS2 in current practice has low sensitivity but high specificity for delirium. Further research is needed to improve routine inpatient monitoring for delirium.