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Schizophr Res. 2008 Nov;106(1):59-69. Epub 2007 Sep 27.

Clinical global impression of cognition in schizophrenia (CGI-CogS): reliability and validity of a co-primary measure of cognition.

Author information

1
UCLA Department of Psychiatry and Biobehavioral Sciences, 300 Medical Plaza, Room 2243, Los Angeles, CA 90095, USA. jventura@ucla.edu

Abstract

BACKGROUND:

Cognitive deficits are core features of schizophrenia that have been associated reliably with functional outcomes and now are a focus of treatment research. New rating scales are needed to complement current psychometric testing procedures, both to enable wider clinical use, and to serve as endpoints in clinical trials.

METHODS:

Subjects were 35 schizophrenia patient-and-caregiver pairs recruited from the UCLA and West Los Angeles VA Outpatient Psychiatry Departments. Participants were assessed with the Clinical Global Impression of Cognition in Schizophrenia (CGI-CogS), an interview-based rating scale of cognitive functioning, on 3 occasions (baseline, 1 month, and 3 months). A computerized neurocognitive battery (Cogtest), an assessment of functioning, and symptom measures were administered at two occasions (baseline and one month).

RESULTS:

The CGI-CogS ratings generally showed a high level of internal consistency (Cronbach's alpha=.69 to .96), adequate levels of inter-rater reliability (ICC's=.71 to .80), and high test-retest stability (ICC's=.92 to .95). Correlations of caregiver and rater global (but not "patient only rating") CGI-CogS ratings with neurocognitive performance were in the moderate range (r's=-.27 to -.48), while most of the correlations with functional outcome were moderate to high (r's=-.41 to -.72). In fact, the CGI-CogS ratings were significantly more correlated with Social Functioning than were objective neurocognitive test scores (p=.02) and showed a trend in the same direction for predicting Instrumental Functioning (p=.06). We found moderate correlations between CGI-CogS global ratings and PANSS positive (r's=.36 to .49) and SANS negative symptoms (r=.41 to .61), but not with BPRS depression (r's=.11 to .13).

CONCLUSIONS:

An interview-based measure of cognition demonstrated high internal consistency, good inter-rater reliability, and high test-retest reliability. Caregiver ratings appear to add important clinical information over patient-only ratings. The CGI-CogS showed moderate validity with respect to neurocognitive performance and functional outcome, and correlations of CGI-CogS with functional outcomes were stronger than correlations of objective neurocognitive performance with functional outcomes. The CGI-CogS appears to offer a reliable and valid method for clinical rating of cognitive deficits and their impact on everyday functioning in schizophrenia.

PMID:
17900866
DOI:
10.1016/j.schres.2007.07.025
[Indexed for MEDLINE]

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