Development of a clinical global impression scale for fatigue

Area of Science:

• Psychiatry
• Clinical Psychology
• Psychometric Evaluation

Background:

• Fatigue is a common symptom in Axis I psychiatric disorders, impacting physical, cognitive, and affective states.
• Accurate assessment of fatigue is crucial for understanding and managing these conditions.

Purpose of the Study:

• To develop and validate two single-item global assessment scales for evaluating fatigue symptoms.
• To assess the reliability and validity of these new scales in a clinical population.

Main Methods:

• Developed modified Clinician Impressions of Fatigue (CGI-S) and Patient Impressions of Fatigue (PGI-S) rating instruments.
• Administered scales to 101 subjects with Major Depressive Disorder, Bipolar disorder, and schizophrenia across two clinic visits.
• Utilized the validated 7-item Modified Hamilton Grading Scale-Cognitive and Physical Functioning Questionnaire (MGH-CPFQ) for convergent validity assessment.

Main Results:

• Both CGI-S and PGI-S for fatigue showed strong correlations with each other (r = 0.75) and with the MGH-CPFQ (CGI-S: r = 0.76; PGI-S: r = 0.62).
• The scales demonstrated temporal stability and convergent validity, with high correlations between CGI-S/PGI-S and MGH-CPFQ (r = 0.83 and 0.73, respectively).
• High internal consistency was observed between independent raters (kappa = 0.971 for CGI-S) and within scales (Cronbach's alpha = 0.998 for CGI-S).

Conclusions:

• The modified CGI and PGI instruments are reliable and valid measures for assessing fatigue in psychiatric patients.
• These scales offer a concise and effective method for evaluating fatigue symptoms in clinical settings.