Keep your participants close, but your informants closer? The added value of high and low contact informants to supplement self-report for the cognitive impairment of schizophrenia.

BACKGROUND: The input of an "informant," a person in the participant's life who can evaluate levels of functioning, can supplement potentially unreliable self-reports in schizophrenia. However, this adds to the complexity of clinical trial design. To evaluate the relative utility of information from informants and participants in a clinical trial context, we compared the participant (self-report), informant, and interviewer ratings for the Schizophrenia Cognition Rating Scale (SCoRS). METHODS: We compared the participant (self-report), informant, and interviewer ratings using paired t-tests, Pearson correlations and Fisher z-transformation and inter-rater reliability (IRR). To assess to importance of informant "closeness," we conducted a categorical analysis split by informant contact (above/below 30 h/week) or relationship to the participant (family or friend). RESULTS: The informant ratings for the SCoRS Total Score had an excellent IRR, (ICC = 0.91), similar to interviewer IRR (0.91). The highest level of impairment was rated by the interviewers, followed by the informant and participant self-reports. The correlation for the SCoRS total between the interviewer and informant (r = 0.92) was significantly larger than between the interviewer and participant self-reports or informant and participant self-reports (both p < 0.01). There were no significant correlations between contact hours and total ratings, and between-group correlations remained highly significant within the categorical analysis subgroups (r > 0.9). CONCLUSIONS: Our results suggest that interviewers relied on informant reports significantly more than the participant self-report, even with an informant who spends as little as 2 h a week with a participant. Future research should assess the relationship of informant ratings with cognition or symptom scales.

Duke Scholars

Author Richard S.E. Keefe Psychiatry & Behavioral Sciences, Behavioral Medicine & Neur ...