Objective: Interview-based measures of cognition may serve as potential coprimary measures in clinical trials of cognitive-enhancing drugs for schizophrenia. However, there is no such valid scale available. Interviews of patients and their clinicians are not valid in that they are unrelated to patients' levels of cognitive impairment as assessed by cognitive performance tests. This study describes the reliability and validity of a new interview-based assessment of cognition, the Schizophrenia Cognition Rating Scale (SCoRS), that involves interviews with patients and informants.
Method: Sixty patients with schizophrenia were assessed with the SCoRS and three potential validators of an interview-based measure of cognition: cognitive performance, as measured by the Brief Assessment of Cognition in Schizophrenia (BACS); real-world functioning, as measured by the Independent Living Skills Inventory; and functional capacity, as measured by the University of California, San Diego, Performance-Based Skills Assessment (UPSA).
Results: The SCoRS global ratings were significantly correlated with composite scores of cognitive performance and functional capacity and with ratings of real-world functioning. Multiple regression analyses suggested that SCoRS global ratings predicted unique variance in real-world functioning beyond that predicted by the performance measures.
Conclusions: An interview-based measure of cognition that included informant reports was related to cognitive performance as well as real-world functioning. Interview-based measures of cognition, such as the SCoRS, may be valid coprimary measures for clinical trials assessing cognitive change and may also aid clinicians desiring to assess patients' level of cognitive impairment.