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Open Access Primary research

A structured interview guide for global impressions: increasing reliability and scoring accuracy for CNS trials

Steven D Targum1*, Celine Houser1, Joanne Northcutt2, Jessica A Little1, Andrew J Cutler2 and David P Walling3

Author Affiliations

1 Clintara LLC, 505 Tremont Street, Boston, MA, 02116, USA

2 Florida Clinical Research Center, LLC 2300 Maitland Center Parkway, Suite 230, Maitland, FL, 32751, USA

3 Collaborative Neuroscience Network, 12772 Valley View Street, Suite 3, Garden Grove, CA, 92845, USA

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Annals of General Psychiatry 2013, 12:2  doi:10.1186/1744-859X-12-2

Published: 31 January 2013

Abstract

Background

The clinical global impression of severity (CGI-S) scale is a frequently used rating instrument for the assessment of global severity of illness in Central Nervous System (CNS) trials. Although scoring guidelines have been proposed to anchor these scores, the collection of sufficient documentation to support the derived score is not part of any standardized interview procedure. It is self evident that the absence of a standardized, documentary format can affect inter-rater reliability and may adversely affect the accuracy of the resulting data.

Method

We developed a structured interview guide for global impressions (SIGGI) and evaluated the instrument in a 2-visit study of ambulatory patients with Major Depressive Disorder (MDD) or schizophrenia. Blinded, site-independent raters listened to audio recorded SIGGI interviews administered by site-based CGI raters. We compared SIGGI-derived CGI-S scores between the two separate site-based raters and the site-independent raters.

Results

We found significant intraclass correlations (p = 0.001) on all SIGGI-derived CGI-S scores between two separate site-based CGI raters with each other (r = 0.768) and with a blinded, site-independent rater (r = 0.748 and r = 0.706 respectively) and significant Pearson’s correlations between CGI-S scores with all MADRS validity comparisons for MDD and PANSS comparisons for schizophrenia (p- 0.001 in all cases). Compared to site-based raters, the site-independent raters gave identical “dual” CGI-S scores to 67.6% and 68.2% of subjects at visit 1 and 77.1% at visit 2.

Conclusion

We suggest that the SIGGI may improve the inter-rater reliability and scoring precision of the CGI-S and have broad applicability in CNS clinical trials.

Keywords:
Inter-rater reliability; Global impressions; Ratings accuracy; Structured interviews