Inter-rater agreement between patient- and proxy-reported cognitive functioning in intensive care unit patients: A cohort study.

Background: Health status, including cognitive functioning before critical illness, is associated with long-term outcomes in intensive care unit survivors. Premorbid data are therefore of importance in longitudinal studies. Few patients can self-report at intensive care admission. Consequently, proxy assessments of patients' health status are used. However, it remains unclear how accurately proxies can report on an intensive care patient's cognitive status.

Objectives: The aim of this study was to examine the agreement between patient- and proxy-reporting of the Cognitive Failures Questionnaire and to compare the agreement between proxy reports using the latter questionnaire and the Informant Questionnaire of Cognitive Decline in the Elderly as a reference.

Methods: The present cohort study is part of a longitudinal multicentre study collecting both patient and proxy data using questionnaires and clinical data from medical records during intensive care unit stays. Agreement on patient and proxy pairs was examined using intraclass correlation coefficient (ICC), Spearman's correlation, percentage agreement, and Gwet's AC1 statistics. Agreement between the proxy-reported questionnaires was examined using percentage agreement and Gwet's AC1 statistics.

Results: In total, we collected 99 pairs of patient-proxy assessments and 158 proxy-proxy assessments. The ICC for the sum scores revealed moderate agreement (n = 99; ICC = 0.59; 99% confidence interval [CI]: [0.30-0.76]) between patient and proxy. Agreement on items was poor (AC1 = 0.13; 99% CI: [0.01-0.24]) to moderate (AC1 = 0.55; 99% CI: [0.43-0.68]). Agreement using cut-off scores (>43) to indicate cognitive impairment was very good (89.9%, AC1 = 0.87; 99% CI: [0.79-0.95]). Agreement between the proxy-reported Cognitive Failures Questionnaire (>43) and the reference questionnaire (≥3.5) was also very good (n = 158; 85%, AC1 = 0.82; 99% CI: [0.74-0.90]).

Conclusions: Proxy assessments of the Cognitive Failures Questionnaire (>43) may be used to indicate cognitive impairment if patients are unable to self-report. Agreement was high between the two questionnaires determined by proxies, showing that these can be used interchangeably to assess cognitive functioning if proxy reporting is needed.