Development of a clinical global impression scale for fatigue.

Physical, cognitive, and affective components of fatigue are often associated with depression and other Axis I psychiatric disorders. We developed two, single item global assessment scales to specifically evaluate symptoms of fatigue. 101 subjects visiting a clinical trial site consented to participate in this reliability and validity study. Diagnoses included Major Depressive Disorder, Bipolar disorder, and schizophrenia. There were two clinic visits during which the modified Clinician and Patient Impressions of Fatigue rating instruments were administered in conjunction with the MGH cognitive and physical functioning questionnaire (MGH-CPFQ), a validated patient-rated 7-item scale. CGI-Severity and PGI-Severity for fatigue were well correlated at two separate visits (p < 0.00005). At visit 1, the mean CGI-S for fatigue was 3.33 ± 1.53 (SD) and the PGI-S for fatigue was 3.57 ± 1.70 (r = 0.75; p = 0.000). At visit 1, the total MGH-CPFQ was 21.66 ± 6.92. Both CGI-S and PGI-S measures for fatigue were highly correlated with the MGH-CPFQ: CGI-S (r = 076; p < 0.00005); PGI-S (r = 0.62; p < 0.00005). Both the PGI-S and CGI-S for fatigue revealed temporal stability and convergent validity for the MGH-CPFQ (r = 0.83 for CGI-S and 0.73 for PGI-S). There was high internal consistency between the two independent CGI raters at visit 2 as demonstrated by a kappa statistic = 0.971 (CGI-S) and 0.868 (CGI-I) and Cronbach's alpha = 0.998 (CGI-S) and 0.941 (CGI-I). As shown here, the modified CGI and PGI instruments for fatigue are reliable measures of fatigue and both measures are validated with the MGH-CPFQ instrument.