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Metadata tables in this guide may be extended in cases where...

From Timing Variables: Collection, Conversion, and Imputation of Dates - CDASH Model 1.2 and Implementation Guide 2.2 - Wiki (cdisc.org)

Timing Variables

Timing variables (e.g., dates) are included in CDASH; they are used to indicate when a particular observation occurred or a period of time when something happened.  

The timing variables included in CDASH Model Section 2.7, Timing (https://www.cdisc.org/standards/foundational/cdash) are available for use in any CRF based on 1 of the 3 general observation classes, except where specific domain restrictions are noted in the SDTMIG. In general, all domains based on the 3 general observation classes should have at least 1 timing variable. In the Events or Interventions general observation class, this could be the start date of the event or intervention. In Findings domains, the collected timing variables generally refer to the date of the test result itself. However, in Findings domains where the result is based on a specimen—such as Laboratory Test Results (LB), Microbiology Susceptibility (MS), Microbiology Specimen (MB), Microscopic Findings (MI), or Pharmacokinetics Concentrations (PC) (Sampling)—the date of the specimen collection associated with the test result is used.

The CDASH Model defines Death Date (DTHDAT) as a timing variable; this is not included as a timing variable in the SDTMIG. It was included as a timing variable in CDASH, as it may be collected on any CRF deemed appropriate by the sponsor, but should only be collected once.

Visits 

Protocols define visits in order to describe assessments and procedures that are to be performed. Visits are typically described using the timing variables VISIT and VISITNUM. The date of the visit is typically collected in the CDASH timing variable VISDAT, which is the date the visit occurred (or started). 

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CDASH Model v1.2 provides a general framework for creating fields to collect information on CRFs and includes the model metadata, which shows the standard variables in the model.

CDASH Model v1.2 provides root-naming conventions for CDASHIG variables, intended to facilitate mapping to SDTMIG variables. The variables defined in the CDASH Model follow the same "--XXXX" naming convention as in the SDTM. The 2 dashes are replaced by the domain code when applied to create the CDASHIG variable. For example, --DOSFRQ is the CDASH Model variable name to for Dosing Frequency per Interval in the Interventions class. When a domain abbreviation is applied (e.g., "CM"), CMDOSFRQ is the CDASHIG variable for the frequency of the concomitant medication use. The CDASH Model includes metadata for variables used in each of the SDTM General Observation classes, Timing variables, Identifier variables, variables for special-purpose domains, and domain-specific variables. See Section 3.5.1 for specific information on this content.  

Mapping instructions in the CDASHIG metadata tables provide more complete guidance than that in the CDASH Model. When domain-level metadata are not available, consult the CDASH Model for SDTM mapping instructions.

Implementers must refer to the CDASH to create alternative text that may be used that meets CDASH conformance rules.

All domains should have at least one timing variable - CDASH section 3.6

Implementers must determine what additional data fields to add to address study-specific and therapeutic area requirements, and applicable regulatory and business practices. See Section 3.4, How to Create New Data Collection Fields When No CDASHIG Field Has Been Defined, for more information on how to create data collection fields that have not already been described in this implementation guide.