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© 2023 2024 Clinical Data Interchange Standards Consortium, Inc. All rights reserved. 

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CDISC specifies how to structure the 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.

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The OGI is a multiple-choice, observer-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 patient, clinician, and observer versions of the global impression instruments (i.e., PGI, CGI and , OGI, respectively). Patient, clinician, and 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 both PGI and CGI instruments of severity, change, and improvement. 
2. The PGI, CGI, and OGI instruments are sometimes referred to by other names:
   1. The 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 OGA instruments) because these instruments do not substantially differ from the analogous PGI, CGI and OGI instruments. Individuals wishing to use the PGA, CGA, or OGA instruments or some other synonymous instruments are directed to CDISC standards developed for the PGI, CGI, and OGI 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 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 --EVLINT field in ISO 8601 format (or --EVINTX, as appropriate) 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. A full list of value sets for the result fields is provided in Section 4, SDTM Mapping Strategy. 

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