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Revision History

© 2024 © 2019 Clinical Data Interchange Standards Consortium, Inc. All rights reserved. 

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This document describes the CDISC implementation of the OGI instruments, which include the Observer Global Impression of Severity (OGI-S), the Observer Global Impression of Change (OGI-C), and the Observer Global Impression of Improvement (OGI-I). These instruments are commonly administered in clinical trials and clinical practices. 

The OGI instruments were initially developed based on the original Clinical Global Impression (CGI) instrument described in the ECDEU Assessment Manual for Psychopharmacology. As previously noted, both (1) the exact wording used in the global item and (2) the values of both the text and numeric components of the response options historically have been generated by sponsors for each of the 3 OGI instruments as implemented in clinical trials or clinical practices. Therefore, no single, standard case report form (CRF) was developed by CDISC for any of the 3 OGI instruments.

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The implementation details for this questionnaire (OGI-S, OGI-C, and OGI-I) are meant to be used in conjunction with the Study Data Tabulation Model Implementation Guide (SDTMIG) but are recorded separately because these instruments may be used in a variety of therapeutic areas. CDISC documentation for all questionnaires, ratings, and scales can be found on the CDISC website at:   https://www.cdisc.org/standards/foundational/qrs.

The CDISC Intellectual Property Policy can be found on the CDISC website at: https://www.cdisc.org/about/bylaws.

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CDISC specifies how to structure the data that data that has been collected in a database, not what should be collected nor how to conduct clinical assessments or implement protocols.

Although the United States Food and Drug Administration (FDA) has provided input with regard to this supplement, this input does not constitute FDA endorsement of any particular instrument.

2 Copyright Status

The OGI instruments are all CDISC believes this instrument to be in the public domain. Indeed, there may be many implementations of each OGI instrument in the public domain, but you should perform your own assessment. CDISC has included the OGI in the CDISC inventory of QRS data standards supplements. Hence, CDISC developed QSTESTCD and QSTEST for each item based on the text on the instrument. There may be many versions of this instrument. CDISC has included the OGI instruments of severity, change, and improvement as part of CDISC data standards. 

Observer Global Impression (OGI) is a generic modification of the CGI instrument for any disease/condition concept use case.

The CDISC documentation for the OGI instruments consists of: (1) standard values (controlled terminology) for QSTESTCD, QSTEST, and QSCAT; (2) a standardized database structure; and (3) some example response option values for each instrument. For the reasons discussed in Section 1, Introduction, CDISC has not developed a standard CRF for any of the 3 OGI instruments to annotate with the CDISC SDTMIG submission values.

Note: CDISC Controlled Terminology is maintained by National Cancer Institute's Enterprise Vocabulary Services (EVS). The most recent version should be accessed through the CDISC website ( at: https://www.cdisc.org/standards/semanticsterminology/controlled-terminology). 

Reference for the OGI: 

Modified from Guy W, ECDEU Assessment Manual for Psychopharmacology. Rockville, MD: U.S. Department of Health, Education, and Welfare;1976.

3 The QS Domain Model

3.1 Assumptions for QS Domain Model

All assumptions and business rules described in the SDTMIG QS domain are applicable to this supplement. Additional assumptions specific to the OGI follow are listed below.

The OGI is a multiple-choice, patientobserver-reported questionnaire. Observer can be anyone other than patient or clinician. The OGI consists of 3 separate items for severity, change, and improvement, each rated on a Likert scale based on the user's choice of responses to the items.

However, no No single (e.g., standardized) version of the OGI-S, OGI-C, or OGI-I currently exists. This is because, for each of these 3 instruments, (1) the specific disease/condition, signs related to the disease/condition, function, and/or functional impact of interest is typically referenced in the wording of the global item; and (2) the response option values on these instruments have not been standardized to date. Indeed, it would be extremely difficult to develop standardized versions of these instruments. Therefore, the implementation described in this document is based on the precedent of (1) sponsors using the OGI-S, OGI-C, and OGI-I as distinct instruments; (2) the specific disease/condition, signs related to the disease/condition, function, and/or functional impact of interest typically being referenced in the wording of the global item; and (3) sponsors determining (a) the exact wording used in the global item and (b) the values of both the text and numeric components of the response options. Instead of creating a separate Questionnaire (QS) Supplement supplement for each of the 3 OGI instruments, the approach taken here was to cover all 3 instruments within 1 a single QS Supplement entitled “Observer Global Impression.”

1. There currently exist both patient, clinician, and clinician observer versions of the global impression instruments (OGI and CGIi.e., PGI, CGI, OGI, respectively). Patient, clinician, and clinician observer assessments of severity, change, and improvement are to be kept separate with respect to how these data are captured in clinical trials and then submitted to the FDA or other regulatory authority for review. A separate supplement exists for the both PGI and CGI instruments of severity, change, and improvement. 
2. The PGI, CGI, and OGI and CGI instruments are sometimes referred to by other names:
   1. The OGI PGI instruments are sometimes referred to as the “Patient Global Assessment” or “PGA” instruments.
   2. The CGI instruments are sometimes referred to as the “Clinical Global Assessment” or “CGA” instruments.
   3. The OGI instruments are sometimes referred to as the “Observer Global Assessment” or “OGA” instruments.
3. CDISC standards will not be developed for synonymous instruments (e.g., for the PGA, CGA, or CGA OGA instruments) because these instruments do not substantially differ from the analogous PGI, CGI and OGI and CGI instruments. Individuals wishing to use the PGA instruments, CGA instrumentsCGA, or OGA instruments or some other synonymous instruments are directed to CDISC standards developed for the PGI, CGI, and OGI and CGI instruments.
4. The 3 OGI instruments (i.e.g., OGI-S, OGI-C, OGI-I) are mutually distinct measures, even when evaluating the same disease/condition within the same clinical study.
5. Assessments made based on a single point in time should be done using the OGI-S. Assessments made in comparison to earlier time points should be done using either the OGI-C or OGI-I.
6. Given that (a) the use of the OGI instruments in a wide variety of therapeutic areas and (b) that the wording of the global item is often disease/condition-specific, this supplement aims to define data standards that are perhaps more general or broader than usual and can be used to report data generated by any version of the OGI instruments implemented in clinical studies. Specifically:
   1. QSSCAT (Subcategory for Question) will be used to capture the specific disease/condition and signs related to the disease/condition, function, and/or functional impact of interest being interest being measured.
   2.  Although general conventions exist for both the numeric and text components of the response options of all 3 OGI instruments, the actual values of the response options for each of these instruments may vary and are to be determined by the sponsor. However, regardless of the exact values of the response options:
      1. Response option text is to be stored in QSORRES (Finding in Original Units).

      2. The numeric component of a response option is to be stored in QSSTRESC (Character Result/Finding in Standard Format) and QSSTRESN (Numeric Finding in Standard Units) as character and numeric values, respectively. Example response option values for QSSCAT, QSORRES, QSSTRESC, and QSSTRESN are provided in Section 4, SDTM Mapping Strategy. Please note that the examples provided in this document are not in any way intended to be prescriptive but rather are provided for illustrative purposes.

   3. Note that an instrument is sometimes referred to as the “Observer Global Impression of Improvement,” or OGI-I, when in fact the instrument is assessing change in either direction and is therefore actually an implementation of the “Observer Global Impression of Change,” or OGI-C. In true implementations of the OGI-I, the response options only allow patients to report either no change or improvement in the disease/condition, functions, functional impacts, or other aspects of the patient’s experience of the disease/condition.
7. In the final dataset submitted to the FDA or other regulatory authority for review, records are to be provided for each study subject, at each assessment time point, for each OGI instrument administered. Within each record, the following variables are expected to be populated: QSCAT, QSTESTCD, QSTEST, QSORRES, QSSTRESC, and QSSTRESN. Records for both missing and non-missing data (assessments) should be included.
8. The CDISC variable QSMETHOD will be used to capture scale type (e.g., Likert scale, verbal rating scales). 
   1. Note that other instruments using the visual analog scale (VAS) and numeric rating scale (NRS) may appear similar to the OGI instruments described in this supplement; however, instruments using either the VAS or the NRS are not the same as the OGI instruments described in this supplement.

9. The time period of evaluation for the OGI is populated in the QSEVLINT --EVLINT field in ISO 8601 format (or QSEVINTX--EVINTX, as appropriate)  when when the evaluation interval can be precisely described as duration. The evaluation interval for the OGI is determined based on the sponsor's stated evaluation interval.

10. Terminology

    1. QSCAT, QSTESTCD, and QSTEST values are included in CDISC controlled terminology.

    2. An example A full list of response value sets for QSORRES, QSSTRESC, and QSSTRESN fields are the result fields is provided in Section 4, SDTM Mapping Strategy. 

3.2 Example for the OGI QS Domain Model

This OGI example shows the terminology used to implement the instrument in the QS domain. The example shows the data for 1 subject collected at visits 1 and 2 for 3 OGI instruments and uses CDISC Controlled Terminology for QSTESTCD, QSTEST, and QSCAT. All original responses results, matching the CRF item response text, are represented with preferred terminology in QSORRES.This result is then transformed into the represented as a standard numeric score in QSSTRESN and as a standard character representation of the standard numeric score in QSSTRESC.

The table below illustrates implementation of represents the items from the OGI instrument dataset qs.

xpt. It represents a given subject’s responses to the global questions posed in the 3 OGI instruments at 2 visits. QSSCAT is populated with the specific underlying construct (e.g., “BACK PAIN”) being evaluated. The values of QSORRES, QSSTRESC, and QSSTRESN are determined by the sponsor and are therefore represented here with values of “X”. Note that for a given construct (e.g., “BACK PAIN”), it is neither required nor typical for all 3 OGI instruments to be administered within the same clinical study. All 3 OGI instruments have been included in the example below for illustrative purposes only. QSMETHOD is used to store the type of scale used.

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This section provides some examples of commonly utilized response option values for each of the 3 OGI instruments (i.e., OGI-S, OGI-C, OGI-I). Please note that these examples are not intended to be prescriptive; they are provided to help clarify some of the concepts and mapping strategies covered in Section 3, The QS Domain Model. The text of the response option selected by a given study subject at a given assessment time point is stored in the SDTM variable QSORRES, and the corresponding numeric score for the selected response option is stored as a numeric value in the SDTM variable QSSTRESN and as a character value in the SDTM variable QSSTRESC. The values of QSORRES, QSSTRESN, and QSSTRESC provided in this section are to be considered as examples only; the actual values of these variables depend on the specific instrument(s) implemented within a given clinical study.

OGI QSTESTCD and QSTEST Controlled Terminology

QSTESTCD = OGI0101   QSTEST = OGI01-Severity   QSMETHOD = LIKERT SCALE 4-POINT

QSTESTCD = OGI0102   QSTEST = OGI01-Change   QSMETHOD = LIKERT SCALE 7-POINT

QSTESTCD = OGI0102   QSTEST = OGI01-Change   QSMETHOD = LIKERT SCALE 7-POINT

QSTESTCD = OGI0103   QSTEST = OGI01-Improvement   QSMETHOD = LIKERT SCALE 7-POINT

End of Document