Grouping variables are a subset of Identifier and Grouping Qualifier variables used to group records in datasets by study, domain, across subjects, by subject, and for a subject. When used per this guidance, grouping variables and their values adhere to the hierarchy below.
The following are expectations for how values in these variables will group of records given their hierarchy.
The optional grouping identifier variable --GRPID may be used in all domains that are based on the general observation classes. --GRPID identifies relationships between records within a USUBJID within a single domain and has no inherent meaning across subjects or across domains. Relationships between observations are defined by assigning the same unique character value to the --GRPID variable for sets of related observations. The values used for --GRPID can be any values the applicant chooses; however, if the applicant uses values with some embedded meaning (rather than arbitrary numbers), those values will be consistent.
Using --GRPID in the general-observation class domains can reduce the number of records in the RELREC, SUPP--, and CO datasets, when those datasets represent relationships/associations for records or values to a "group" of general observation class records.
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