National Institute of Mental Health. CGI: Clinical
Global Impressions. In: Guy W, Bonato RR, eds. Manual for the ECDEU
Assessment Battery.2. Rev ed. Chevy Chase, Md: National Institute of
Mental Health; 1970:12-1-12-6.
Appropriate for: All categories of psychiatric patients
Administered by: Patient's psychiatrist or other trained rater
Time to complete: 5 minutes
Summary:
CGI is a three-item scale used to assess treatment response in psychiatric
patients. They are:
Severity of Illness; Global Improvement; Efficacy Index. Item 1 is rated
on a seven-point scale (1=normal to 7=extremely ill); item 2 on a
seven-point scale (1=very much improved to 7=very much worse); and item 3
on a four-point scale (from 'none' to 'outweighs therapeutic effect').
The Severity of Illness item requires the clinician to rate the severity
of the patient's illness at the time of assessment, relative to the
clinician's past experience with patients who have the same diagnosis.
Considering total clinical experience, a patient is assessed on severity
of mental illness at the time of rating according to: normal (not at all
ill); borderline mentally ill; mildly ill; moderately ill; markedly ill;
severely ill; or extremely ill.
The Global Improvement item requires the clinician to rate how much the
patient's illness has improved or worsened relative to a baseline state.
Compared to condition at baseline, a patient's illness is compared to
change over time, and rated according to: very much improved; much
improved; moderately improved; minimally improved; no change; minimally
worse; moderately worse; much worse; or very much worse.
Benefits of the CGI scale:
- Robust - CGI has proved to be a robust measure of efficacy in drug
treatment trials
- Simplicity - the scale is clinically understandable
- Sensitive to change
Challenges of the CGI scale:
- Subjective - to a certain degree, severity of illness as rated on
the CGI scale is based on the rater's subjective views of symptom
severity, which can vary between raters and make consistent
interpretation of CGI scores problematic in practice
- Lack of structure - the CGI scale is administered at initial patient
assessment and at least once when treatment/change in treatment has
been initiated. Additional assessments are conducted at the discretion
of the clinician. Again, this implies a certain degree of subjectivity
in terms of the timing and frequency of CGI assessment which may make
retrospective interpretation difficult
- In-depth knowledge required - although the CGI scale is quickly
administered, particularly for the Global Improvement scale it is
paramount for the rater to know the patient. If a clinical history is
not available, then the tool can not be utilised
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