Concordant with an increased emphasis on consumer engagement, the Patient Global Impression Scale of Improvement (PGI-I) is commonly used as an outcome measure in studies evaluating the efficacy of treatments in medical and psychiatric conditions with subjective symptom domains. The current study evaluated the agreement between PGI-I and Clinician Global Impression Scale of Improvement (CGI-I) ratings and convergent validity of PGI-I among individuals with bipolar or major depressive disorders.

Data were derived from three double-blind, placebo-controlled, multicentre studies conducted from 2007 to 2015 among adult individuals (N = 472). Clinicians were asked to rate participants symptoms using the CGI-I as well as severity of depression by the Montgomery-Åsberg Depression (MADRS), quality of life (Q-LES-Q), social and occupational functioning (SOFAS), and functional impairment (LIFE–RIFT). Participants were asked to assess their symptom improvement with the PGI-I. Bland-Altman agreement plots and Intra-class correlations were used to evaluate agreement, and Spearman correlation coefficients were implemented to examine convergent validity. Sub-group analyses for disorder type (bipolar and major depression) were performed.

There was high agreement between the PGI-I and CGI-I ratings across follow-up time points (weeks 2, 4, 6, 8, 12, 16, 20, 24, and 28). Similar results were observed in male only and female only data and after adjustment for age and gender. Both PGI-I and CGI-I ratings were robustly positively correlated with MADRS, and LIFE-RIFT and negatively correlated with SOFAS and Q-LES-Q, supporting the convergent validity of the PGI-I. Sub-group analyses for bipolar and major depressive disorder showed similar findings.

Our findings support the utility of the PGI-I as a participant rated measure of global improvement among individuals with bipolar or major depressive disorders.