In this observational study, participants will not receive any study treatment or experimental intervention. The study procedures include daily delirium assessments and routine clinical data collection.

Family members will complete one FAM-CAM assessment each day as soon as possible after the ICU visiting period ends, usually between 15:30 and 16:00. The family member will fill out the assessment form, and study staff will check the form for completeness and accuracy and record the time the assessment is completed.

Nurses will complete one ICDSC assessment each day as soon as possible after the ICU visiting period ends, usually between 15:30 and 16:00. The nurse will record the assessment result and the time the assessment is completed.

Trained research staff will complete one CAM-ICU assessment within a prespecified time window, close to the time of the family FAM-CAM assessment and the nurse ICDSC assessment. The CAM-ICU result and assessment time will be recorded.

This outcome will measure the level of agreement among the three assessment methods in the same patient and within the same general time frame.During the ICU phase, paired assessment data will be created according to the pairing rules described for the primary outcome. The results of FAM-CAM, ICDSC, and CAM-ICU will be classified as either "positive" or "negative."Agreement will be evaluated using Cohen's kappa coefficient as the main measure. The overall agreement rate, positive agreement rate, and negative agreement rate will also be reported as additional measures, together with 95% confidence intervals.

This outcome measure will evaluate the effect of older age, defined as age 65 years or older; low education level, defined as primary school education or below; language or dialect communication barriers, recorded as present or absent; and family members' delirium knowledge questionnaire scores on disagreement among delirium assessments.

Assessment disagreement is defined as inconsistent delirium classification among the family-completed FAM-CAM, nurse-completed ICDSC, and CAM-ICU completed by trained research staff in the same patient and within a similar assessment time frame.

The study will compare the proportion of disagreement events across different subgroups and will use regression analysis to evaluate the strength of association between these factors and assessment disagreement. Results will be reported as odds ratios with 95% confidence intervals.