How to Extend Metadata

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If data are in scope for a domain defined in this guide, but not all data can be collected using the domain's collection fields, then fields may be added from the CDASH Model or created using guidance below. Prior to adding fields from the CDASH Model or considering a new field, confirm that none of the fields in the domain will fit the need. Fields may be added from the CDASH Model or created only when data are different in nature and are not in scope for existing domain fields.

Once confirmed, determine whether adding a field from the CDASH Model will fit the need. If adding a field from the CDASH Model meets the need, then a new field will not be created. New fields will only be created for when data are not in scope for a field defined in the CDASH Model.

The overall process for extending metadata is as follows:

Adding Fields from the CDASH Model

Example 2: A study has subjects' blood samples sent to a central lab, which analyzes the samples and sends results to the sponsor via electronic data transfer. In a second study, the samples are analyzed locally and results are captured on a CRF. The laboratory results from both studies are stored in the SDTMIG Laboratory Test Results (LB) domain.
The Question Text and Prompt columns in the CDASH Model metadata provide different variations in the recommended text for asking the question on a CRF. For each question, the sponsor may elect to either use the Question Text or the Prompt on the CRF. Some text is presented using brackets [ ], parentheses ( ), and/or incorporating forward slashes. These different formats are used to indicate how the Question Text or Prompt may be modified by the sponsor.
1. Example: The CDASH variable --PERF, from the CDASH Model, has the following Question Text and Prompt.
  Question Text: [Were any/Was the] [--TEST/ topic] [measurement(s)/test(s)/examination(s)/specimen(s)/sample(s)] [performed/collected]?
  Prompt: [--TEST/Topic] [Measurement(s)/Test(s)/Examination(s)/Specimen(s)/Sample(s)] [Performed/Collected]?
  The sponsor wants to add a question to a CRF that asks whether a lab specimen was collected, using a Yes/No response.
  The sponsor selects the CDASH variable --PERF and adds the appropriate domain code. LBPERF
  Use either the Prompt or the Question Text on the CRF.
  Question Text: Was the laboratory specimen collected?
  - In the first set of brackets, the text option "Was the" is selected, as the study required only 1 lab test to be performed. [Were any/Was the]
  - In the second set of brackets, the text used is "laboratory," which is the topic of interest. [--TEST/Topic (laboratory)]
  - In the third set of brackets, the text option "specimen," without the optional "s," is selected. [measurement(s)/test(s)/examination(s)/specimen(s)/sample(s)]
  - In the fourth set of brackets, the text option "collected" is selected. [performed/collected]
  Prompt: Laboratory Specimen Collected
  - In the first set of brackets, the text used is the topic of interest (i.e., laboratory). [--TEST/Topic (Laboratory)]
  - In the second set of brackets, the text option "specimen," without the optional "s," is selected. [Measurement(s)/Test(s)/Examination(s)/Specimen(s)/Sample(s)]
  - In the third set of brackets, the text option "collected" is selected. [Performed/Collected]

Creating New Fields

When creating a new data collection field, determine whether the data will be used for an operational use case, such as data cleaning, or are actual data to be represented in a tabulation dataset. In general, new data collection fields (not already defined in the CDASH Model) will fall in one of following categories:

A field used for operational, Data Cleaning purposes only.
A field used to collect data that have Direct Mapping to a target variable in the tabulation dataset.
A field used to collect data that have No Direct Mapping to a target variable in the tabulation dataset.

The table below provides implementation guidance aligned with both the category of the field and target variable.

Num	Field Category	Target Tabulation Variable	Implementation
1	Data Cleaning	NA	The field --YN with Question Text "Were there any [interventions/events/findings]?" can be used for this purpose. Replace the two dashes (--) with the two-character domain code and create the Question Text or Prompt using generic Question Text or Prompt from the CDASH Model as a base. Always create custom data-cleaning/operational variables using consistent naming conventions.
2	Direct Mapping	Yes	If a value can be collected exactly as it will be reported in the tabulation dataset (i.e., same value, same data type, same meaning, same controlled terminology), the tabulation variable name will be used as the data collection variable name in the operational database to streamline the mapping process. Extensions may be appended if needed to create a unique variable name in the collection database. Any collection variable whose meaning is the same as tabulation variable will align with tabulation variable and the meaning will not be modified for data collection.
3	No Direct Mapping	Yes	If a value cannot be collected in alignment with the tabulation dataset variable (e.g., collected data type is different from the data type in the corresponding tabulation variable) or if the tabulation variable is derived from the collected value, then the operational database should use a collection variable with a different name from tabulation variable into which it will be mapped.
3	No Direct Mapping	No	If a field does not align with a tabulation variable, a unique name should be assigned based on applicant business rules using CDASH naming fragments (e.g., --DAT, --TIM) as appropriate and CDISC variable naming fragments, found in Section x.x, CDISC Variable-naming Fragments, where possible.

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How to Extend Metadata