Clinical Global Impression CGI
Clinical Global Impression CGI overview
Creator and Context
The Clinical Global Impression (CGI) is a pair of single item clinician ratings: one for how ill the person is now, and one for how much they have changed since treatment began.
It was published in the NIMH ECDEU Assessment Manual for Psychopharmacology, edited by William Guy, in 1976. It is one of the most widely used measures in psychiatric research, and it takes under a minute.
Presenting Conditions
The CGI has two components:
CGI-Severity: how mentally ill is the person at this time, considering the clinician's total experience with this population
CGI-Improvement: compared with their condition before treatment began, how has the person changed
Both are single items with no subscales.
Administration
Clinician rated, after a clinical evaluation, in under a minute. The rating draws on all available information: interview, records, family, teachers or care workers.
Both items are rated on a 7 point scale. The recall window is the past 7 days including the day of the visit. CGI-Improvement is anchored to the week before treatment started, not to the previous appointment.
Desired Audience
Any psychiatric condition, any age. It requires a rater who is experienced with the condition in question, because the rating is explicitly relative to that experience.
Two questions and under a minute is a very cheap way to capture the clinician's overall judgement, and it is a judgement no symptom scale replaces. It is also the anchor most commonly used to establish what a change on another instrument actually means.
Considerations
There are no universally accepted scoring guidelines for the seven anchor points. They were designed to rest on clinical judgement. The CGI has anchors, not validated cut offs.
CGI-Improvement is anchored to baseline, not to the previous visit. This is the most common implementation error.
Severity and improvement can move independently. Do not derive one from the other.
Rating quality depends entirely on the rater's experience with the population. There is no training free validity.
Ratings should not incorporate side effects.
How to score the Clinical Global Impression CGI
Conducting the assessment
The clinician selects one of seven anchors for severity, and one of seven for improvement.
Interpretation
CGI-Severity anchors: 1 normal, not at all ill; 2 borderline mentally ill; 3 mildly ill; 4 moderately ill; 5 markedly ill; 6 severely ill; 7 among the most extremely ill patients.
CGI-Improvement anchors: 1 very much improved; 2 much improved; 3 minimally improved; 4 no change from baseline; 5 minimally worse; 6 much worse; 7 very much worse.
There is no summing and no total. Each item stands alone.
Clinical Considerations
Anchor improvement to the start of treatment, every time.
Record severity and improvement separately, and expect them to diverge.
Use it alongside a symptom measure. Where the clinician's global rating and the instrument disagree, that is worth investigating.
Clinical Global Impression CGI use cases
Capturing the clinician's global judgement of severity and change
Anchoring the interpretation of change on other measures
Defining response and remission in trials
Brief outcome capture in routine care
Category
Feedback
Research Summary
Guy, W. (Ed.). (1976). ECDEU Assessment Manual for Psychopharmacology. Rockville, MD: US Department of Health, Education, and Welfare.
Busner, J., & Targum, S. D. (2007). The Clinical Global Impressions Scale: Applying a research tool in clinical practice. Psychiatry (Edgmont), 4(7), 28 to 37.
Spearing, M. K., Post, R. M., Leverich, G. S., et al. (1997). Modification of the Clinical Global Impressions (CGI) Scale for use in bipolar illness. Psychiatry Research, 73(3), 159 to 171.
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