Relationships between global assessment of functioning and other rating scales in clinical trials for schizophrenia

The relationship between the Global Assessment of Functioning (GAF) with other scales in schizophrenia has rarely been investigated. A systematic literature search was conducted to identify articles that reported the GAF score together with scores in the Positive and Negative Syndrome Scale (PANSS), Clinical Global Impression (CGI) or Brief Psychiatric Rating Scale (BPRS), using MEDLINE, EMBASE and PsycINFO, with keywords of schizophrenia, clinical trial and global assessment of functioning (last search 30 June 2013). Correlational analyses with weighting by the study participant numbers across these rating scales were performed. In 40 clinical trials (n=8000) that reported cross-sectional data on the GAF and PANSS, a significant but modest correlation was noted (Pearson׳s r=-0.401, p<0.0001). Furthermore, a correlation between the GAF and CGI-severity (CGI-S) at study baseline in 38 studies (n=11,315) was robust (r=-0.893, p<0.0001). In longitudinal studies, changes in the GAF scores were negatively correlated with those in the PANSS as well as CGI-S scores (p<0.0001 for both). Data on the BPRS were all statistically significant although relatively scarce. While optimal degree of concordance is undetermined among psychiatric scales that are presumed to be measuring different but overlapping constructs, this study found significant correlations in the GAF and CGI-S or PANSS, both cross-sectionally and longitudinally. The GAF-CGI-S relationship was especially tighter, making it a reliable clinical indicator.