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

CDISC does not modify questionnaires, ratings, and scales (QRS) instruments to meet Clinical Data Acquisition Standards Harmonization (CDASH) case report form (CRF) standardsThere is no standard case report form (CRF) available for this instrument. CDISC created this 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  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 QRS documentation CDISC questionnaires, ratings, and scales (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 Fredriksson reference article.
      
   2. The Fredrikkson Fredriksson 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 agreed to use these responses as the data standard.
   3. The Fredrikkson Fredriksson 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 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.
      

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