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

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

CDISC does not modify questionnaires, ratings, and scales (QRS) instruments to meet Clinical Data Acquisition Standards Harmonization (CDASH) case report form (CRF) standards.

The representation of data collected for this clinical classification 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 clinical classification instrument are meant to be used in conjunction with the SDTMIG. All CDISC QRS documentation packages can be found on the CDISC website at: https://www.cdisc.org/foundational/qrs.

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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 have chosen to use these responses as the data standard.explain trunk score
   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 have chosen 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 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.
      

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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.

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