Performance and validation of two ICU delirium assessment and severity tools; a prospective observational study

Background: The clinical statistical performance of the Confusion Assessment Method Intensive Care Unit (CAM-ICU, including CAM-ICU-7) and Intensive Care Delirium Screening Checklist (ICDSC) have rarely been studied. Additionally, delirium severity is often not measured due to a lack of validation of delirium assessment tools.

Objective: The aim was to determine the statistical performance of both delirium assessment tools in daily practice, and the correlation with the gold standard Delirium Rating Scale (DRS)-R98, for delirium severity.

Research method: CAM-ICU-7 and ICDSC, performed by nurses were compared with the DRS-R98 assessed by delirium experts, twice weekly. Within a time-window of one hour all assessments were independently performed.

Design: A prospective observational study performed between October and December 2020.

Main outcome measures: Sensitivity, specificity, positive and negative predictive value of both tools was determined. The correlation between DRS-R98 and CAM-ICU-7 and ICDSC was used for validation of delirium severity.

Results: In total, 104 CAM-ICU-7 and 105 ICDSC assessments in 86 patients were compared with the DRS-R98. For the CAM-ICU-7 and ICDSC, respectively, the sensitivity was 90% and 95%, the specificity was 92.4% and 92.3%. The positive predictive value was 0.76 and 0.80, and negative predictive value was 0.77 and 0.97. Correlation of the CAM-ICU-7 score and ICDSC score with the DRS-R98 score was 0.74 (95% CI 0.64-0.81) and 0.70 (95%CI 0.59-0.79; both p < 0.001), respectively.

Conclusion: Both CAM-ICU-7 and ICDSC demonstrated good statistical performance and correlated well with the delirium severity tool DRS-R98.

Implications for clinical practice: Nurses can either use the CAM-ICU(-7) or the ICDSC in their practice, both are accurate in delirium diagnosis. Total CAM-ICU-7 and ICDSC score reflects delirium severity well; the higher the score, the more severe the delirium. This enables nurses to gauge the impact of their interventions and enhance the well-being of patients experiencing delirium by minimizing distressing occurrences.