CDISC CRT-DDS 1.0

Purpose

The CDISC CRT-DDS standard defines the metadata structures in a machine-readable XML format. These metadata structures are used to describe tabulation and analysis data sets and variables for regulatory submissions. The XML schema that is used to define the metadata structures in an XML format is based on an extension to the CDISC Operational Data Model (ODM).

Release Date

CDISC CRT-DDS, Final Version 1.0, February 10, 2005

Regulatory Basis

(Source: CDISC Case Report Tabulation Data Definition Specification)

In 1999, the FDA standardized the submission of clinical and non-clinical data and metadata in a set of eSubmission guidelines to include metadata descriptions of the data sets and columns within a Data Definition Document (define.pdf). In 2003, the FDA published a set of guidance documents on receiving electronic product applications per the International Conference on Harmonisation (ICH) electronic Common Technical Document (eCTD) specifications. In these specifications, the FDA expanded the acceptable file types to include the XML format.

CDISC CRT-DDS 1.0 Reference Standard

Overview

The domain and column metadata that constitute the SAS representation of CDISC CRT-DDS 1.0 are derived from the global standards library in these formats:

as empty data sets (using the utility macro cst_createTablesForDataStandard)
as table metadata for 39 data sets (reference_tables in the standard metadata folder [see the example in reference_tables (CDISC CRT-DDS 1.0)])
as column metadata for 176 columns in the 39 data sets (reference_columns in the standard metadata folder

reference_tables (CDISC CRT-DDS 1.0)
AnnotatedCRFs	ItemGroupAliases	MDVLeafTitles
CLItemDecodeTranslatedText	ItemGroupDefItemRefs	MUTranslatedText
CodeListLitems	ItemGroupDefs	MeasurementUnits
CodeLists	ItemGroupLeaf	MetaDataVersion
ComputationMethods	ItemGroupLeafTitles	Presentation
DefineDocument	ItemMURefs	ProtocolEventRefs
ExternalCodeLists	ItemQuestionExternal	RCErrorTranslatedText
FormDefArchLayouts	ItemQuestionTranslatedText	Study
FormDefItemGroupRefs	ItemRangeCheckValues	StudyEventDefs
FormDefs	ItemRangeChecks	StudyEventFormRefs
ImputationMethods	ItemRole	SupplementalDocs
ItemAliases	ItemValueListRefs	ValueListItemRefs
ItemDefs	MDVLeaf	ValueLists

As a general rule, the SAS representation of the CDISC CRT-DDS standard is patterned to match the XML element (data set) and attribute (column) structure of define.xml. For example, for CDISC SDTM, domain-level metadata is represented by a define.xml ItemGroupDef element. This metadata is captured in the ItemGroupDefs SAS data set. The TE domain metadata is shown in this code:

<ItemGroupDef OID="docroot.IG.TE"
    Name="TE"
    Repeating="No"
    IsReferenceData="Yes"
    Purpose="Tabulation"
    def:Label="Trial Elements"
    def:Structure="One record per planned element"
    def:DomainKeys="STUDYID,ETCD"
    def:Class="Trial Design"
    def:ArchiveLocationID="ArchiveLocation.te">
    !-- All ItemRefs would be listed here -->
    <def:leaf ID="ArchiveLocation.te"
    xlink:href="te.xpt"> <def:title>te.xpt</def:title>
  </def:leaf>
</ItemGroupDef>

The TE domain metadata is shown in this table.

Sample Data Set Representation: ItemGroupDefs.sas7bdat
Column	Value
OID	IG.TE
Name	TE
Repeating	No
IsReferenceData	Yes
SASDatasetName	TE
Domain	TE
Origin
Role
Purpose	Tabulation
Comment	Elements are the building blocks of Arms. Arms consisting of Elements are the paths subjects will follow.
Label	Trial Elements
Class	Trial Design
Structure	One record per planned element
DomainKeys	STUDYID, ETCD
ArchiveLocationID	Location.TE
FK_MetaDataVersion	MDV.1

Note: Empty or null attributes are not typically included in the XML file.

The highly structured nature of CDISC CRT-DDS data requires that any mapping to a relational format include a large number of data sets, with foreign key relationships to help preserve the intended non-relational object structure. In the SAS Clinical Standards Toolkit, foreign key relationships are enforced when validating the CDISC CRT-DDS data sets.

Field lengths in the CDISC CRT-DDS data sets are consistent by core data type. CDISC has not specified any limit to the length of most character fields. Arbitrary lengths have been chosen by data type. These lengths are listed in this table. In the table, standard data types are distilled into core data types. To be safe, larger lengths have been chosen to ensure that no data loss occurs in the SAS Clinical Standards Toolkit pre-installed data sets. Production tables might be compressed using SAS mechanisms to preserve disk space.

CDISC CRT-DDS Default Lengths by Data Type
Type Name	Length	Description
oid	128	A unique object identifier or a reference
text	2000	A character field that can accommodate a large number of characters
name	128	A descriptive identifier
value	512	An item of collected or reference data
path	512	An absolute or relative file system path or URL

Note: CRT-DDS and ODM use slightly different lengths.

CDISC CRT-DDS SAS Data Set Construction

The SAS Clinical Standards Toolkit CDISC CRT-DDS reference standard supports reading and representing in SAS a define.xml file, building a define.xml file, and validating the structure and content of the SAS representation of a define.xml file. In addition, the structural integrity of the define.xml file is validated, and a define.pdf file can be generated. To support this functionality, supplemental files include these global standards library files:

A SAS format catalog (crtddsct.sas7bcat) in the formats folder provides valid values for selected columns in the 39 data sets of the SAS representation.
The Validation Master data set in the validation/control folder contains the superset of checks validating the structure and content of the 39 data sets.
The Messages data set in the messages folder provides error messaging for all Validation Master checks.
SAS code in the macros folder provides CDISC CRT-DDS-specific code that augments code that is provided in the primary SAS Clinical Standards Toolkit autocall library (!sasroot/cstframework/sasmacro).
The style sheet folder contains the define1-0-0.xsl and define-v1-updated-html.xsl XSL style sheets.

The define1-0-0.xsl style sheet was the original style sheet published by CDISC in 2005. It can be found at http://www.cdisc.org/define-xml.

The define-v1-updated-html.xsl style sheet was used in the 2013 update to the first CDISC SDTM/ADaM Pilot Project ( http://www.cdisc.org/sdtm-adam-pilot-project).

A define.xml file can be rendered in a human-readable form if it contains an explicit XML style sheet reference, such as a reference to the default style sheet.