Validity of the IQCODE-CA: An informant questionnaire on cognitive decline modified for a cardiac arrest population

To examine the psychometric properties of a modified version of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE), for a cardiac arrest population (IQCODE-CA).

The IQCODE-CA, a 26-item observer-reported questionnaire, was completed by informants, defined as relatives or close friends, of 268 out-of-hospital cardiac arrest (OHCA) survivors who participated in the Target Temperature Management trial in a scheduled follow-up 180±14days after OHCA. Survivors completed the Mini Mental State Examination (MMSE), the Rivermead Behavioural Memory Test (RBMT) and the Hospital Anxiety and Depression Scale (HADS). An exploratory factor analysis was performed. Associations between IQCODE-CA results and demographic variables along with other instruments were calculated. Area under the curve (AUC) ratios were evaluated to examine discrimination.

The IQCODE-CA measured one factor, global cognitive decline, with high internal consistency (ordinal α=0.95). Age, gender or education did not influence the IQCODE-CA score. Associations with performance-based measures of global cognitive function as well as anxiety and depression ranged from small to moderate (r_s=-0.29 to 0.38). AUC ratios ranged from fair to good (0.72-0.81). According to the MMSE and RBMT, the optimal cut-off score to identify cognitive decline on the IQCODE-CA was 3.04. Using this value, 53% of the survivors were under the cut-off.

The IQCODE-CA identified a large amount of survivors with possible cognitive problems, making it useful when screening for cognitive decline post-CA. Due to lower AUC ratios than desired, additional performance-based measures should be used to improve the overall screening methodology.