Derivation and Validation of a Severity Scoring Method for the 3‐Minute Diagnostic Interview for Confusion Assessment Method‐‐Defined Delirium

Objectives To derive and validate a method for scoring delirium severity using a recently validated, brief, structured diagnostic interview for Confusion Assessment Method ( CAM )‐defined delirium (3D‐ CAM ) and to demonstrate its agreement with the CAM Severity short form ( CAM ‐S SF ) as the reference standard. Design Derivation and validation analysis in a prospective cohort study. Setting Two academic medical centers. Participants Individuals aged 70 and older enrolled in the Successful Aging after Elective Surgery Study undergoing major elective noncardiac surgery (N = 566). Measurements The sample was randomly divided into a derivation dataset (n = 377) and an independent validation dataset (n = 189). These datasets were used to develop a severity scoring method using the 3D‐ CAM based on the four‐item CAM ‐S SF (3D‐ CAM ‐S) and evaluate agreement between the 3D‐ CAM ‐S and the traditional CAM ‐S SF using weighted kappa statistics. Results A method for scoring severity using 3D‐ CAM items was developed that achieved good agreement with the CAM ‐S SF in the derivation dataset (κ = 0.94, 95% confidence interval ( CI ) = 0.93–0.95). The 3D‐ CAM ‐S achieved nearly identical agreement in the independent validation dataset (κ = 0.93, 95% CI = 0.92–0.95), and 100% of 3D‐ CAM ‐S scores were within 1 point of the CAM ‐S SF score in both datasets. The 3D‐ CAM ‐S also strongly predicts clinical outcomes. Conclusion A newly developed method for scoring delirium severity using the 3D‐ CAM (the 3D‐ CAM ‐S) has excellent agreement with the CAM ‐S SF . This new methodology enables clinicians and researchers using the 3D‐ CAM for surveillance to measure delirium severity and monitor its course simultaneously by tracking changes over time. The 3D‐ CAM ‐S expands the utility of the 3D‐ CAM as an important tool for delirium recognition and management.