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The Related Records (RELREC) special-purpose dataset is used to describe relationships between records for a subject and relationships between datasets. In both cases, relationships represented in RELREC are collected relationships. The RELREC dataset should be used to represent either:

• Explicit relationships, (e.g., concomitant medications taken as a result of an adverse event); or
• Information of a nature that necessitates using multiple datasets and that may need to be examined together for analysis or proper interpretation.  

It is not necessary to use the RELREC dataset to identify associations from data in the Supplemental Qualifiers (SUPP--) datasets or the Comments (CO) dataset to their parent general-observation class dataset records or special-purpose domain records, as both these datasets include the key variable identifiers of the parent record(s) that are necessary to make the association.

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RELREC will not be used to represent

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relationships already represented in Supplemental Qualifier (SUPP–) datasets for nonstandard variables or Comments (CO) for 

Subject records or datasets expressing a relationship are specified using the key variables STUDYID, RDOMAIN (the domain code of the record or dataset in the relationship) with IDVAR (the variable that identifies the related record(s)). Each record in the RELREC special-purpose dataset contains keys that identify a record (or group of records) and an identifier for the relationship which is stored in the RELID variable. The value of RELID is chosen by the applicant and it is recommended that applicants use a standard system or naming convention for RELID (e.g., all letters, all numbers, capitalized).

Relationships Between Records for a Subject

Relationships between records for a subject are specified using the key variables STUDYID, RDOMAIN, and USUBJID, along with IDVAR and IDVARVAL (the value of the identifying variable). IDVARVAL will contain the value of the variable described in IDVAR. Single records can be related by using a unique-record-identifier variable such as --SEQ in IDVAR. Groups of records can be related by using grouping variables such as --GRPID in IDVAR.  Using --GRPID can be a more efficient method of representing relationships in RELREC when relating a single or group of records in one dataset to a group of records in another dataset. Variable RELTYPE will not be used when relating records for a subject and is only used when representing relationships between datasets. The value of RELID will be identical for all related records within USUBJID.

Relationships Between Datasets

Relationships between datasets are represented using a single record for each related dataset that identifies the key(s) of the dataset that can be used to relate the respective records. Relationships between datasets are specified using the key variables STUDYID, RDOMAIN, and IDVAR only. The values of variables USUBJID and IDVARVAL will be null as relationships between specific subject records will not be null identified. The variable RELTYPE

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will identify the type of relationship between the datasets (e.g., a one-to-one or parent-child relationship). The allowable values for RELYPE are ONE and MANY

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per CDISC Controlled Terminology. This information defines how a merge/join would be written, and what would be the result of the merge/join. The possible combinations are:

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The Related Records (RELREC) special-purpose dataset is used to describe relationships between records for a subject and relationships between datasets. In both cases, relationships represented in RELREC are collected relationships. The RELREC dataset should be used to represent either:

• Explicit relationships (e.g., concomitant medications taken as a result of an adverse event); or
• Information of a nature that necessitates using multiple datasets.

Relationships Between Records for a Subject

A relationship is defined by adding a record to RELREC for each record to be related and by assigning a unique character identifier value for the relationship. Each record in the RELREC special-purpose dataset contains keys that identify a record (or group of records) and the relationship identifier, which is stored in the RELID variable. The value of RELID is chosen by the applicant but must be identical for all related records for a subject. It is recommended that the applicant use a standard system or naming convention for RELID (e.g., all letters, all numbers, capitalized).

Records expressing a relationship are specified using the key variables STUDYID, RDOMAIN (the domain code of the record in the relationship), and USUBJID, along with IDVAR and IDVARVAL. Single records can be related by using a unique-record-identifier variable such as --SEQ in IDVAR. Groups of records can be related by using grouping variables such as --GRPID in IDVAR. IDVARVAL would contain the value of the variable described in IDVAR. Using --GRPID can be a more efficient method of representing relationships in RELREC, such as when relating an adverse event (or events) to a group of concomitant medications taken to treat the adverse event(s).

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