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© 2020 Clinical Data Interchange Standards Consortium, Inc. All rights reserved. 

1 Introduction

This document describes the CDISC implementation of the Psoriasis Area and Severity Index (PASI) instrument.

There is no standard CRF available for this instrument. CDISC created this case report form (CRF) to represent the instrument, which is in the public domain. This is not an endorsement of the instrument. The creation of this instrument was based on input from PASI subject matter experts. Sponsors may create this instrument’s CRF using their style guidelines, but they need to maintain the wording and order of the questions/items and responses as described on the CRF.

The representation of data collected for this instrument is based on the Study Data Tabulation Model Implementation Guide (SDTMIG) Disease Response and Clin Classification (RS) domain model, which can be found on the CDISC website at: https://www.cdisc.org/standards/foundational/sdtmig.

These specific implementation details for this instrument are meant to be used in conjunction with the SDTMIG. All CDISC questionnaires, ratings, and scales (QRS) documentation packages can be found on the CDISC website at: https://www.cdisc.org/foundational/qrs.

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

1.1 Representations and Warranties, Limitations of Liability, and Disclaimers

This document is a supplement to the SDTMIG for Human Clinical Trials and is covered under Appendix F of that document, which describes representations, warranties, limitations of liability, and disclaimers. Please see Appendix F of the SDTMIG for a complete version of this material.

CDISC specifies how to structure the data that has been collected in a database, not what should be collected or how to conduct clinical assessments or protocols.

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

2 Copyright Status

This instrument is in the public domain. CDISC has included the PASI in the CDISC library of QRS data standards supplements. Hence, CDISC developed RSTESTCD and RSTEST for each item based on the actual text on the clinical classification. There may be many versions of this instrument in the public domain or copyrighted. CDISC has chosen to use this version as the data standard.

The CDISC documentation of this instrument consists of: (1) controlled terminology, (2) standard database structure with examples, and (3) CRF(s) annotated with the CDISC SDTMIG variables with submission values.

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

References for the Psoriasis Area and Severity Index (PASI):

• Fredriksson T, Pettersson U. Severe Psoriasis--Oral Therapy with a New Retinoid. Dermatologica. 1978;157(4):238-244.

• Feldman SR, Krueger GG. Psoriasis assessment tools in clinical trials. Ann Rheum Dis. 2005;64(Suppl 2):ii65–ii73.

3 The RS Domain Model

3.1 Assumptions for the RS Domain Model

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

The PASI is a tool used to assess the severity of psoriasis. The PASI breaks the body up into 4 sections (i.e., head, trunk, upper extremity, lower extremity) and assesses symptom severity and the percentage of each area affected by psoriasis. The symptoms are rated on a 5-point scale and the area is rated on a 7-point scale. Subscores for each section of the body and a total score are also captured.

1. The scale points for the symptoms (i.e., erythema, infiltration, desquamation) include a numeric rating (0-4) and a definition of what is represented by the rating (e.g., 0 = "None"). For the PASI, RSORRES is populated with the text description while the numeric rating is represented in the standardized character and numeric result variables RSSTRESC and RSSTRESN.

   1. CDISC created a CRF based on input from subject-matter experts and the original Fredrikkson reference article.
      
   2. The Fredrikkson article is the original reference for the PASI; however, the Symptom Score response choices have changed over time to "None", "Slight", "Moderate", "Severe", and "Very Severe" as supported in the Feldman reference above. CDISC subject matter experts agreed to use these responses as the data standard.
   3. The Fredrikkson article has an apparent error showing the trunk percentage of the total score being multiplied by 20% in the text on the bottom of page 2; however in the formula highlighted on the page 3, and in other reference articles including Feldman, 30% is used for the trunk percentage of the total score. CDISC subject matter experts agreed to use 30% for the trunk percentage of the total score.
2. The scale points for the area include a numeric rating (0-6) and a definition of what is represented by the rating (e.g., 0 = "No Involvement"). For the PASI, RSORRES is populated with the text description while the numeric rating is represented in the standardized character and numeric result variables RSSTRESC and RSSTRESN.
   

3. The PASI instrument includes subscores and a total score that are considered as captured data on the CRF and are not considered as derived in the example below. These scores are considered as captured data when provided as part of Electronic Data Transfer (eDT) and are not considered as derived in the example below.

   1. If operationally defined by the sponsor, it is the sponsor's responsibility to set the --DRVFL flag based on their eCRF process to derive subtotals and total scores. An investigator-derived score written on a CRF will be considered a captured score and not flagged. When subtotal and total scores are derived by the sponsor, the derived flag (--DRVFL) is set to Y. However, when the subtotal and total scores are received from a central provider or vendor, the value would go into --ORRES and --DRVFL would be null (see SDTMIG Section 4.1.8.1, Origin Metadata for Variables).

4. Terminology

   1. RSCAT, RSTESTCD, and RSTEST values are included in CDISC Controlled Terminology.

   2. A full list of value sets for the result field is provided in Section 4, SDTM Mapping Strategy.
      

3.2 Example for the PASI RS Domain Model

The PASI example below shows the terminology used to implement the instrument in the RS domain. This example shows the data for 1 subject collected at the baseline visit for the PASI instrument. The example uses CDISC Controlled Terminology for RSTESTCD, RSTEST, and RSCAT. All original results are represented with preferred terminology in RSORRES. This result is then transformed into the standard numeric score in RSSTRESN and a character representation of the standard numeric score in RSSTRESC.

The table represents the items from the PASI form. The total PASI score is shown in row 29.

4 SDTM Mapping Strategy

This section is used for reference regarding the CRF data capture and to understand the alignment of the instrument to the SDTM RS domain. It also provides guidance on how the result variables (RSORRES, RSSTRESC, and RSSTRESN) should be populated.

RSTESTCD = "PASI0101" RSTEST = "PASI01-Head (H): Erythema (E)"

RSTESTCD = "PASI0102" RSTEST = "PASI01-Head (H): Infiltration (I)"

RSTESTCD = "PASI0103" RSTEST = "PASI01-Head (H): Desquamation (D)"

RSTESTCD = "PASI0108" RSTEST = "PASI01-Trunk (T): Erythema (E)"

RSTESTCD = "PASI0109" RSTEST = "PASI01-Trunk (T): Infiltration (I)"

RSTESTCD = "PASI0110" RSTEST = "PASI01-Trunk (T): Desquamation (D)"

RSTESTCD = "PASI0115" RSTEST = "PASI01-Up Extrem (U): Erythema (E)"

RSTESTCD = "PASI0116" RSTEST = "PASI01-Up Extrem (U): Infiltration (I)"

RSTESTCD = "PASI0117" RSTEST = "PASI01-Up Extrem (U): Desquamation (D)"

RSTESTCD = "PASI0122" RSTEST = "PASI01-Low Extrem (L): Erythema (E)"

RSTESTCD = "PASI0123" RSTEST = "PASI01-Low Extrem (L): Infiltration (I)"

RSTESTCD = "PASI0124" RSTEST = "PASI01-Low Extrem (L): Desquamation (D)"

RSTESTCD = "PASI0105" RSTEST = "PASI01-Head (H): Area Score"

RSTESTCD = "PASI0112" RSTEST = "PASI01-Trunk (T): Area Score"

RSTESTCD = "PASI0119" RSTEST = "PASI01-Up Extrem (U): Area Score"

RSTESTCD = "PASI0126" RSTEST = "PASI01-Low Extrem (L): Area Score"

End of Document